JSCS Vol 65, No. 5-6
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J. Serb. Chem. Soc. 65(5-6)281-283(2000)
UDC 92/486.1/
Professor Slobodan V. Ribnikar - On
the occasion of his 70th birthday
This issue of the Journal of the Serbian Chemical Society is
dedicated to Professor Slobodan V. Ribnikar and to his activities in the field
of molecular spectroscopy, on the occasion of his 70th birthday. Among his
numerous activities it is certain that Prof. Ribnikar left a noticeable impact
on the local activities bound to molecular spectroscopy. A number of
participants of the 12th Conference on General and Applied Spectroscopy decided
that their papers be included in this issue of the Journal.
Prof. S. Ribnikar was born in Belgrade in 1929,
where he attended elementary and secondary schools. He studied at the Faculty
of Science, Belgrade University, in the years from 1948 to 1952, majoring in
physical chemistry. His first employment was as research assistant at the Boris
Kidric Institute of Nuclear Sciences in Vinca nearBelgrade. He received the
doctoral degree at the Faculty of Science in 1958. During the period 1959 to
1967 he spent four years in the Chemistry Department of the Brookhaven National
Laboratory, Upton, N. Y., USA. In 1968 he was appointed as associate professor
at the Faculty of Science in Belgrade. He served as director of the Department
of Chemical and Physicochemical Sciences and later as vice dean of the Faculty.
As full professor he retired on pension in 1994, but he still participates in
many activities of the Faculty. In 1983, be was elected as a corresponding
member of the Serbian Academy of Sciences and Arts and as a full member in
1994. He is an honorary member of the Serbian Chemical Society and a member of
the Society of Physical Chemists of Serbia. Among others, he is a bearer of the
October Prize of the city of Belgrade.
His first and lasting interest in scientific
research was the chemistry of isotopes. His first research in 1952, supervised
directly by Professor Pavle Savi}, concerned catalysts active in hydrogen -
water isotope exchange. The results were reported at the Conference on Peaceful
Uses of Atomic Energy held in Geneva in 1954. It turned out that the most
active catalyst in this research was identical to the one already in use in
heavy water plants in the USA and Canada, but kept classified. A similar event
took place at another conference in 1957 where the results of S. Ribnikar on
boron isotope separation were reported simultaneously with the ones coming from
the USA, England, Sweden and the USSR.
A group for stable isotope separation founded by
S. Ribnikar at the Vinca Institute was for a long time one of the leading
centers of its kind in Europe. It is still active today. Significant contributions
to the processes of separation of isotopes of hydrogen, lithium, nitrogen,
carbon and even uranium resulted from the research of this group.
While working at the Brookhaven National
Laboratory, Prof. Ribnikar collaborated very fruitfully with Dr. Jacob
Bigeleisen, one of the leading scientists in the field of isotope chemistry.
Supplementing Dr. Bigeleisen, who was a theoretician, Prof. Ribnikar, using his
experimental skills, succeeded in checking and prov- ing a number of
theoretical suppositions in isotope chemistry, e.g., the inequality of the
vapor pressures of the three isomeric dideuteroethylenes.
At the Faculty of Science, in the Department of
Physical Chemistry, a significant part of his activity was devoted to teaching.
Being an exceptional lecturer, he became one of the most esteemed and beloved
professor, among the students. He taught regularly Radiochemistry and up to his
retirement he held the Chair of Radiochemistry and Nuclear Chemistry.
Simultaneously he introduced a new subject named the Physical Chemistry of
Fluids, dealing mainly with intermolecular forces, for which he wrote a
textbook. He also lectured Molecular Spectrochemistry and Atomistics at the
undergraduate and Vibrational Spectroscopy at the postgraduate level. He
mentored a number of doctoral and masters dissertations. A great number of
diploma works was supervised by him.
Prof. Ribnikar's experience in calculating
isotope effects from vibrational frequencies resulted in the introduction of
infrared spectroscopy at both the Vinca Instituteand the Faculty. This field
has since been actively pursued by his students and collaborators. He also
introduced the use of infrared lasers for the separation of isotopes, and the
use of the UV emission lines of the mercury arc to separate carbon
isotopes. The separation factors for 13C in the carbamate - carbon
dioxide exchange system were also elaborated in detail.
Prof. Ribnikar devoted a number of years to the
pbolem of investigating hydrogen bonds in molecular complexes of ethers and
ketones with either alcohols or silanols. Models of such interactions were
given and quantitative data governing the stability, which are of importance in
silicon-organic chemistry, were obtained.
While investigating experimentally the discrete
infrared emission of solids and liquids, Prof. Ribnikar developed a unique
theory explaining the structure of these spectra.
In the field of molecular physics Prof. Ribnikar
carried out detailed experimental investigations of the infrared and Raman
spectra of simple molecules in order to determine whether the anharmonicity of
molecular vibrations change on condensation of dissolution. Despite quite
different spectra, it was concluded that the zero-order frequencies are not
affected.
Even though the intention was to report on the
activities of Prof. Ribnikar in the field of spectroscopy only, his activities
in other fields: analyses of trituim in reactor moderators, a project of
removing tritium from reactor fuels and waste waters etc, must inevitably be
mentioned, as must a lengthy investigation of the possible presence of element
113 in natural thallium minerals.
The results of the scientific work of Prof.
Ribnikar have been published in 72 scientific papers and in a great number of
conference proceedings.
Next to the purely scientific publication of
Prof. Ribnikar, his contributions to other related activities must also be
mentioned. For ten years (1975-1985) he was editor of the chemistry journal
"Glasnik Hemijskog dru{tva Beograd", which, in 1984, was renamed to
the present title "The Journal of the Serbian Chemical Society".It is
largely due to his merit that the Journal, published at that time predominantly
in Serbo-Croatian, became known to the general public.
Being actively involved in editing the journal,
he compiled and published the "Serbo-Croatian_English Dictionary,
Chemistry and Related Sciences" containing some 10000 entries, and later a
list of 2000 etymologically explained chemical terms. In addition, he published
21 shorter texts on Serbocroatian professional terminology.
It is difficult to list all the activities of
Prof. Ribnikar. I hope no significant items have been omitted. It is a fact
that we had and still have with us an exceptional man and intellectual, a
physical chemist and molecular spectroscopist, who has left significant traces
in our surroundings. I recall the words of a well known French scientist who
said: "Professor Ribnikar is a true intellectual, one of ones rarely
encountered today. I am only an artisan. I am glad to have met him".
Ubavka B. Mioc
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J.Serb.Chem.Soc.
65(5-6)285-301(2000)
UDC 543.42/.51:537.635:539.144.4
JSCS-2746
Original scientific paper
Two-dimensional exchange
spectroscopy revisited: Accounting for the number of participating spins
NENAD JURANIC, ZSOLT ZOLNAI and SLOBODAN MACURA
Department of Biochemistry and
Molecular Biology, Mayo Graduate School, Mayo Clinic and Mayo Foundation,
Rochester, Minnesota, 55905 U.S.A.
(Recieved 18 December
1999)
The magnetization exchange between two groups of
equivalent spins each having different populations and overall relaxation rates
has been analyzed. The results suggest that either the spin population
difference or the overall relaxation rate difference in an exchange spectrum
can produce cross-peaks with volumes larger than that of the corresponding
diagonal line. This is important for interpretation of the magnetization
exchange between water and macromolecular protons where both the population
differences and auto-relaxation rate differences can be very large. Theoretical
predictions of peak volume evolution were experimentally verified in the
intermolecular magnetization exchange between the water and labile amide proton
in a model system N-acetylglycine/water.
Keywords: NMR, exchange spetroscopy, chemical
exchange, hydrogen exchange.
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J.
Serb. Chem. Soc. 65(5-6)303-310(2000)
UDK 546.15:543.51/.53
JSCS-2747
Original scientific paper
Iodine molecule covalente excited
states as determined by threshold electron spectrometry
MILAN KUREPA*,** and JOZO JURETA*
*Institute of Physics, P.O. Box 68,
11081 Belgrade and
**Serbian Academy of Sciences and Arts, Kneza Mihaila 35,
Belgrade, Yugoslavia
(Received 16 December
1999, revised 1 March 2000)
The iodine molecule has been investigated by a
threshold electron spectrometer in the incident electron energy range from 1.00
eV to 3.5eV. From the threshold electron spectrum contributions for excitation
of three states known from optical spectrometry have been subtracted. The
remaining signal has been interpreted by four curves similar in shape to those
in absorption otpical spectroscopy into antibonding energy states. The detected
maxima have been attributed to the following valence excited states of the
iodine molecule: 3P2u(2u), 3P0u-(0u-),
3P2g(2g), and 3P1g(1g),
respectively. With the knowledge of the energy ranges within which the signal
from a particular state appears, the predicted values of equilibrium distances
of iodine atom nuclei and estimated values of vibrational transition frequency
potential energy curves have been constructed, too.
Keywords: electron impact, iodine molecule,
excitation, valence states.
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J.Serb.Chem.Soc.
65(5-6)311-314(2000)
UDC 537.5:661.862.84
JSCS-2748
Original scientific paper
Magnetism of F centers; indication
of an antiferromagnetic phase transition in potassium-electro-sodalite
LJILJANA DAMJANOVIC, GALEN D. STUCKY and VOJISLAV I. SRDANOV
Department of Chemistry, University
of California at Santa Barbara, CA 93106, USA
(Received 10 December
1999, revised 25 February 2000)
Temperature-dependent EPR data of
potassium-electro-sodalite (PES), K8[Al6Si6O24](e-)2,
are consistent with the occurrence of an antiferromagnetic phase transition at
71±2 K. PES is a Mott insulator which contains an unpaired electron in every
sodalite cage. The same transition in sodium-electro-sodalite occurs at a
considerably lower temperature (42 K), indicating that the exchange interaction
among localized electrons is stronger in PES. PES is obtained by the inclusion
of one potassium atom in every cage of potassium sodalite. The 27Al
MAS NMR resonance of PES is shifted downfield in respect to diamagnetic
potassium-sodalite, K6[Al6Si6O24].
The NMR shift is due to unpaired electrons and is caused by hyperfine Fermi
contact interaction.
Keywords: sodalite, F center, AF transition.
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J.
Serb. Chem. Soc. 65(5-6)315-322(2000)
UDC 66.062:543.064:541.51
JSCS-2749
Original scientific paper
Contribution to a study of organic
solvent addition on trace determination by FAAS
MARIJA R. TODOROVIC, IVANKA HOLCLAJTNER-ANTUNOVIC*, VERICA A.
MILICEVIC and RANDJEL MIHAJLOVIC**
Faculty of Chemistry, University of
Belgrade, P.O. Box 158, YU-11001 Belgrade,
*Faculty of Physical Chemistry, University of Belgrade, P.O. Box
137, YU-11001 Belgrade and
**Faculty of Science, University of Kragujevac, P.O.Box 60,
YU-34000 Kragujevac, Yugoslavia
(Received 27 October
1999, revised 25 February 2000)
The influence of the presence of an organic
solvent on the determination of trace elements by flame atomic absorption
spectrophotometry (FAAS) was investigated under different experimental
conditions. The obtained results show that the effect of organic solvents on
the signal intensities depends not only on the physical properties of the
solution but on the analyte properties too. The extent of the effect is also
very dependent on the construction of the nebulization system as well as on the
stoichiometric flame composition. These facts indicate the very complex
mechanism of the effect and demonstrate the essential importance of taking care
strictly of the experimental parameters and conditions when using organic
solvents in analytical practice.
Keywords: solvent addition, trace
determination, FAAS.
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J.
Serb. Chem. Soc. 65(5-6)323-329(2000)
UDC 546.815:543.42/5:663.2
JSCS-2750
Original scientific paper
Spectrochemical determination of lead in wines
MIRJANA TRIPKOVIC, MARIJA TODOROVIC*, IVANKA
HOLCLAJTNER-ANTUNOVIC**, SLAVICA RAZIC***, ALEKSANDRA KANDIC* and DRAGAN
MARKOVIC
Institute of Physics, P. O. Box 57,
YU-11000 Belgrade,
*Faculty of Chemistry, University of Belgrade, P. O. Box 158,
YU-11000 Belgrade,
**Faculty of Physical Chemistry, University of Belgrade, P. O. Box
137, YU-11000 Beograde,
***Faculty of Pharmacy, University of Belgrade, P. O. Box 146,
YU-11000 Belgrade, Yugoslavia
(Received 27 October
1999, revised 24 February 2000)
The determination of lead in wines of different
origin was performed by means of atomic emission spectroscopy with argon
stabilized DC. U-shaped arc and electrothermal atomic absorption spectrometry.
The comparison of the results obtained by the direct and standard addition
method has indicated the presence of a depressive effect of the complex organic
matrix. The effect is avoided successfully by mineralization, as well as by dissolution
of the samples. Thus, a relative simple but precise and sensitive method
involving the application of a stabilized arc and photoelectric detection with
time integration of the emission signals is recommended for the determination
of low concentrations of lead in wines. The complex organic matrix was
investigated by recording the IR spectra of different wine fractions.
Keywords: lead, U-shaped arc, GFAAS, organic
matrix.
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J.
Serb Chem. Soc. 65(5-6)331-338(2000)
UDS 543.422:546.18:613.26/.29
JSCS-2751
Original scientific paper
An atomic absorption spectrometric
method for the determination of phosphorus in foodstuffs using the bismuth
phosphomolybdate complex
RANDJEL P. MIHAJLOVIC, VESNA M. KALJEVIC, RADMILA M. DZUDOVIC,
ZORKA D. STANIC and LJILJANA V. MIHAJLOVIC
Faculty of Science, University of
Kragujevac, YU-34000 Kragujevac, Yugoslavia
(Received 27 October
1999, revised 16 March 2000)
A new indirect AAS method using the bismuth
phosphomolybdate complex for the determination of phosphorus in foodstuffs is
suggested. The bismuth phosphomolybdate complex in acid medium was extacted
with isobutyl methylketone and the phosphorus was determined through bismuth in
an air/acetylene flame by utilising the 223.06 nm resonance line of bismuth.
The interference caused by antimony and titanium can be neglected in the
presence of excess of bismuth. The detection limit of the method is 0.008 mg/mL
of phosphorus.
Keywords: Atomic absorption spectrometry,
phosphorus determination, foodstuffs, bismuth phosphomolybdate complex.
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J. Serb. Chem. Soc. 65(5-6)339-344(2000)
UDC 615.3:628.513:535.243/.247
JSCS-2752
Original scientific paper
Simultaneous determination of
compounds in Septalen pellets by derivative spectrophotometry
MIRJANA MEDENICA, DARKO IVANOVIC* and ANDJELIJA MALENOVIC*
Institute of Physical Chemistry,
Faculty of Pharmacy, Vojvode Stepe 450, YU-11001 Belgrade and
*Institute of Drug Analysis, Faculty of Pharmacy, Vojvode Stepe
450, YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999, revised 28 February 2000)
In this paper, a second-derivative
spectrophotometric method of assaying Septalen pellets (Krka, Novo Mesto, Slovenia),
which contain lidocaine 1 mg, and cetrimonium bromide 2 mg, is described.
Lidocaine, 2-(diethylamino)-N-(2,6-dimethyl-phenyl)-acetamide, is a local
anesthetic with pronounced antiarhythmic and anticonvulsant properties.
Cetrimonium bromide, N,N,N-trimethyl-l-hexadecanaminium bromide, is a topical
antiseptic and cleansing agent. Lidocaine was determined at 250 nm using the
"zero crossing" technique because the signals of centrimonium bromide
and the colour ingredient are zero at this wavelength. Cetrimonium bromide was
determined by correction of the peak amplitude at 215 nm according to
lidocaine. In choosing the optimal magnitudes for the simultaneous
determination of both drugs, the following criteria were considered: (1) the
linearity of the calibration graphs as given by the correlation coefficients,
(2) the intercept, (3) the sensitivity as given by the regression coefficient,
(4) the degree of interference in the derivative measurement by the presence of
the other compound, as given by the relative percent error and by the relative
recovery, and (5) the reproducibility, as given by the coefficient of
variation, calculated by recording the second-derivative spectra.
Keywords: second-derivative
spectrophotometry, zero-crossing method, method with correction, lidocaine,
cetrimonium bromide, Septalen pellets.
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J.
Serb. Chem. Soc.65(5-6)345-352(2000)
UDC 546.593:535.243:546.32'15"
JSCS-2753
Original scientific paper
Spectrophotometric investigations
of the reaction between gold(III) and potassium iodide
VESNA VASIC, SUZANA PREMOVIC, MIRA CAKAR*, BOJAN RADAK and GORDANA
MILOVANOVIC**
Vinca Institute of Nuclear Sciences,
P. O. Box 522, YU-11001 Belgrade,
*Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450,
YU-11001 Belgrade and
**Faculty of Chemistry, University of Belgrade, Studentski trg 15,
YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999, revised 24 February 2000)
The equilibria of the complex formation between
AuCl4-n(OH)n- and I- was studied
spectrophotometrically in aqueous solutions containing KI:Au(III)<2
in the acidity range from 1 M HCl to pH 7 at 25°C. From the hydrogen ion and
Cl- ion dependence of the absorption spectra, it was found that AuCl2I2-
and Au(OH)2I2- complexes were formed. The
equilibrium constants of complex formation were determined.
Keywords: Au(III), iodine, complexes, aqueous
solutions.
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J.
Serb. Chem. Soc. 65(5-6)353-359(2000)
UDC 547.595.1/.2/.8:543.422:551.521.17
JSCS -2754
Original scientific paper
Solvent effect on electronic
absorption spectra of cyclohex-1-enylcarboxylic and
2-methylcyclohex-1-enylcarboxylic acids
JASMINA B. NIKOLIC, GORDANA S. USCUMLIC and VERA V. KRSTIC
Department of Organic Chemistry,
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4,
YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999)
The ultraviolet absorption spectra of
cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were
determined in six protic and nine aprotic solvents in the wavelength range from
200 to 400 nm. The position of the lmax of the two examined
acids showed that the ultraviolet absorption maximums of
cyclohex-1-enylcarboxylic acid were at consistently longer wavelengths in
protic solvents than those of methylcyclohex-1-enylcarboxylic acid. The
opposite was true in aprotic solvents. In order to explain the obtained
results, the ultraviolet absorption frequencies of the electronic transitions
in the carboxy carbonyl group of the examined acids were correlated using a
total solvatochromic equation of the form: n = n0 + sp* + aa +
bb, where p* is a measure of the solvent polarity, b represents the scale
of solvent hydrogen bond acceptor basicities and a represents the scale of
solvent hydrogen bond donor acidities. The correlation of the spectroscopic
data was carried out by means of multiple linear regression analysis. The
opposing solvent effects on the ultraviolet absorption maximums of the two
examined acids were discussed.
Keywords: cyclohex-1-enylcarboxylic acid,
2-methylcyclohex-1-enylcarboxylic acid, ultraviolet absorption maximum, protic
and aprotic solvents.
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J.
Serb. Chem. Soc. 65(5-6)361-369(2000)
UDC 5394/.196
JSCS-2755
Original scietific paper
A simplified approach to the
vibrational self-relaxation of simple molecules through convolution of their
velocities
SCEPAN S. MILJANIC and DUSAN D. GOLOBOCANIN*
Faculty of Physical Chemistry,
University of Belgrade, P.O. Box 137, YU-11001 Belgrade and
*Department of Physical Chemistry, Vinca Institute of Nuclear
Sciences, P.O. Box 522, YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999)
A theoretical approach has been developed for
computing collisional self-relaxation probabilities of the first excited level
in the lowest vibrational mode of simple molecules. The bending (n2) vibration in triatomic molecules, in which the average translational
and rotational velocities are of the same order of magnitude, was examined. The
approach was based on the assumption that both the velocities should be taken
into account as a convolution of the corresponding Maxwell's distribution
functions. The model was checked for the SO2 molecule in the
temperature range from 130-1100 K. The calculated temperature dependence curve
(the Landau-Teller plot) exhibits a minimum at about 150 K. The data obtained
is discussed in relation to some experimental results. The comparison indicates
that the problem was treated in correct manner. Some additional aspects of the
relaxation, like intermolecular interactions and the steric factor, are also
briefly considered. It is believed that this approach offers quite a good basis
for further improvements of theoretical treatments.
Keywords: vibrational relaxation, molecular
collisions, convolution, velocity distribution, SO2.
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J.
Serb. Chem. Soc. 65(5-6)371-379(2000)
UDC 547.854:544.6/.62:66.084
JSCS -2756
Original scientific paper
Infrared study of some
2-substituted-6-hydroxy-4-pyrimidine carboxylic acids. Correlation with
MO-calculations
LJUBINKA J. BOGUNOVIC, UBAVKA B. MIOC*, BRATISLAV Z. JOVANOVIC and
IVAN O. JURANIC**
Faculty of Technology and
Metallurgy, University of Belgrade, P.O. Box 494, YU-11001 Belgrade,
*Faculty of Physical Chemistry, University of Belgrade, P.O. Box
137, YU-11001 Belgrade and
**Faculty of Chemistry, University of Belgrade P.O. Box 158,
YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999, revised 22 February 2000)
The IR spectra of a series of
2-substituted-6-hydroxy-4-pyrimidine carboxylic acids (substituent = OH, SH, CH3, CH3S and NH2) were studied from the
aspect of the influence of the subsitutent on the polarizability of some bonds,
keto-enol tautomerism and hydrogen bond formation. The spectra were taken using
solids due to the low solubility of the acids. Theoretical calculations were
done using the MNDO-AM1 semiempirical molecular-orbital method. The stabilities
of various tautomers were calculated simulating the dielectric continuum using
the COSMO facility of the MOPAC program package. Theoretical calculations were
made for all the possible tautomers of the 2-substituted-6-hydroxy-4-pyrimidine
carboxylic acids. For the most stable isomers, the vibrational spectra were
calculated. For the majority of the compounds the most stable isomer was
identified having the structure 2-Y-6-oxo-4-carboxy-3H-pyrimidine. Besides this
structure, for the 2-amino-, and 2-methyl- derivatives the zwitterionic forms
have very similar stability. The 2-hydroxy compound is most stable as the
2,6-dioxo-1H, 3H isomer. The calculated vibrations for the compounds with a
single stable structure correlate very well with the experimental frequencies.
For the 2-methyl- and 2-amino- compounds the correlation is considerably less
satisfactory. The most probable reason for this deviation is the existence of
two or more tautomets in equilibrium. The correlation of the measured
frequencies and the pKa values of the acids, indicate that the same
tautomers exist in the solid state and in the solution.
Keywords: IR-spectra, pyrimidine-4-carboxylic
acids, calculation of vibrational frequencies, AM1-MNDO.
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J.
Serb. Chem. Soc. 65(5-6)381-389(2000)
UDC 621.3.038.8/.029:535.243
JSCS-2755
Original scientific paper
A frequency stabilized waveguide CO2-laser for
photoacoustic spectroscopy of gases
GORDANA M. OSTOJIC, BOJAN B. RADAK and LJUBICA T. PETKOVSKA
Vinca Institute of Nuclear
Sciences, Department of Physical Chemistry, P.O. Box 522, YU-11001 Belgrade,
Yugoslavia
(Received 27 October
1999, revised 25 February 2000)
A theoretical model of a waveguide CO2-laser was made to
optimize the dimensions of the waveguide tube and resonator, i.e., to
obtain the best mode structure while maximizing the output power. The results
were used to design and build the laser itself around a quartz waveguide tube
of 25.5 cm and 3 mm inner diameter. A simple, low-cost, and efficient VMOS
based current stabilization was applied, which stabilized the current to within
±0.5 %. The working laser frequency selection and/or frequency stabilization
was controlled by a piezo micro-positioner, which was coupled with an output
power meter via a PC computer and driven by self-made software developed
for the purpose. The experimental test of the laser showed good agreement with
the model.
Keywords: CO2-laser, photoaconstic
spectroscopy, gases.
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J.
Serb. Chem. Soc. 65(5-6)391-397(2000)
UDC 546.34'882"/54-31/:548.55:535.84
JSCS-2756
Original scientific paper
The crystallization and optical
properties of LiNbO3 single crystals
ALEKSANDAR GOLUBOVIC, RADOS GAJIC*, SLOBODANKA NIKOLIC, STEVAN
DJURIC** and ANDREJA VALCIC***
Institute of Chemistry, Technology and
Metallurgy, Njegoseva 12, YU-11000 Belgrade,
*Institute of Physics, Pregrevica 118, P.O. Box 57, YU-11001
Belgrade,
**Faculty of Mining and Geology, Djusina 7 P. O. Box 162, YU-11001
Belgrade, and
***Faculty of Technology and Metallurgy, Karnegijeva 4, YU-11000
Belgrade, Yugoslavia
(Received 27 October
1999, revised 21 February 2000)
LiNbO3 single crystals were grown by the Czochralski
technique in an air atmosphere. The critical crystal diameter Dc = 1.5 cm and the
critical rate of rotation wc = 35 rpm were calculated from the dynamic of
fluids equations for buoyancy-driven and forced convections under which the
shape of the melt/crystal interface changed. The domain inversion was carried
out at 1473 K using a 10 min 3.75 V/cm electric field. The obtained crystals
were cut, polished and etched to determine the presence of dislocations and
single domain structures. The lattice parameters a = 0.51494 nm, c
= 1.38620 nm and V = 0.3186 nm3 were determined by X-ray
powder diffraction. The optical properties were studied by infrared
spectroscopy in the wave number range 20 - 5000 cm-1. With
decreasing temperature, an atypical behaviour of the phonon modes, due to the
ferroelectric properties of LiNbO3 single crystal, could be seen. The optical
constants were calculated by Kramers-Kronig analysis and the value of the
critical temperature was estimated. The obtained results are discussed and
compared with published data.
Keywords: Czochralski technique, lithium
niobate, single crystal, optical properties.
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J. Serb. Chem. Soc.
65(5-6)399-406(2000)
UDC 661.878/54-381/:543.42
JSCS-2758
Original scientific paper
A spectroscopic investigation of
12-tungstophosphoric acid alkali salts
UBAVKA B. MIOC, MARIJA R. TODOROVIC*, SNEZANA M.
USKOKOVIC-MARKOVIC**, ZORAN P. NEDIC and NADA S BOSNJAKOVIC
Faculty of Physical Chemistry,
University of Belgrade, P. O. Box 137, YU-11001 Belgrade,
*Faculty of Chemistry, University of Belgrade, P. O. Box 158,
YU-11001 Belgrade and
**Faculty of Pharmacy, University of Belgrade, P. O. Box 146,
YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999)
In this paper the latest results of our
continuing investigation of heteropoly acids and their salts are reported.
Specially attention was paid to the influence of cations on the dynamic
equilibrium of protonic species, as well as on the structure of the host
lattice itself, i.e., the Keggin anions. The investigations were done by IR and
Raman spectroscopy within the range of 1200-40 cm-1.
Keywords: IR spectra, Raman spectra,
12-tungstophosphoric acid, alkali salts of 12-tungstophosphoric acid, Keggin
anion.
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J.
Serb.Chem. Soc. 65(5-6)407-415(2000)
UDC 546.562'78''185-325''':543.424:541.6
JSCS-2759
Original scientific paper
Structural modifications of Cu(II)
12-tungstophosphoric acid salit studied by IR and Raman spectroscopy
UBAVKA B. MIOC, MARIJA TODOROVIC*, SNEZANA USKOKOVIC-MARKOVIC**,
ZORAN NEDIC, VOJISLAV STAMENKOVIC and TAMARA CAJKOVSKI***
Faculty of Physical Chemistry,
University of Belgrade, P. O. Box 137, YU-11001 Belgrade,
*Faculty of Chemistry, University of Belgrade, P. O. Box 158,
YU-11001 Belgrade,
**Faculty of Pharmacy, University of Belgrade, P. O. Box 146,
YU-11001 Belgrade and
***Vinca Institute of Nuclear Sciences, P. O. Box 522, YU-11001
Belgrade, Yugoslavia
(Received 27 October
1999, revised 24 February 2000)
In this paper local processes and structural
phase transformations of the copper salt of 12-tungstophosphoric acid are
investigated. The structural phase transformations were followed through bands,
characteristic for the host lattice, in the IR and Raman spectra. The results
of these investigations, as well as those of XRPD analysis and impedance
measurements as a function of temperature show that some local processes
provoke the change in the secondary structure of the Keggin anions.
Keywords: IR spectra, Raman spectra, heteropoly
compounds, proton conductors, phase transformations.
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J.
Serb. Chem. Soc. 65 (5-6)417-430(2000)
UDC 543.42:66,084
JSCS-2760
Original scientific paper
Vibrational spectroscopic and
quantum theoretical study of host-guest interactions in clathrates: I. Hofmann
type clathrates
BILJANA MINCEVA-SUKAROVA, LILJANA ANDREEVA, LJUPCO PEJOV and
VLADIMIR M. PETRUSEVSKI
Institute of Chemistry, Faculty of
Science, University "St Cyril & Methodius", Arhimedova 5, P. O.
Box 162, MK-91001 Skopje, Republic of Macedonia
(Received 16 December
1999)
Hofmann type clatharates are host-guest
compounds with the general formula M(NH3)2M'(CN)4·2G, in which M(NH3)2M'(CN)4 is the host lattice and
G is benzene, the guest molecule. In previous studies, host-guest interactions
have been investigated by analyzing the RT and LNT vibrational (infrared, far
infrared and Raman) spectra of these clathrates. All the observed changes in
the vibrational spectra of these clathrates are referred to a host-guest
interaction originating from weak hydrogen bonding between the ammonia hydrogen
atoms from the host lattice and the p electron cloud of the guest (benzene) molecules.
In order to obtain an insight into the relative importance of the local
crystalline field vs. the anharmonicity effects on the spectroscopic properties
of the guest species upon enclathration, as well as to explain the observed
band shifts and splittings, several quantum theoretical approaches are
proposed.
Keywords: Hofmann clathrates, host-guest
interactions, vibrational spectroscopy, vibrational Stark effect, perturbation
theory.
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J.
Serb. Chem. Soc. 65(5-6)431-438(2000)
UDC 547.622:547.222:543.42
JSCS-2761
Original scientific paper
Mass spectrometry analysis of
polychlorinated biphenyls: chemical ionization and selected ion chemical
ionization using methane as a reagent gas
TATJANA M. VASILJEVIC, MILA D. LAUSEVIC and RAYMOND E. MARCH*
Faculty of Technology and
Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Yugoslavia
and
*Trent University, Peterborough, ON K9J 7B8, Canada
(Received 27 October
1999, revised 3 March 2000)
In the present paper a quadrupole ion trap mass
spectrometer, coupled with a gas chromatograph, was used to compare the
electron impact ionization (EI) and chemical ionization (Cl) technique, in
terms of their selectivity in polychlorinated biphenyls (PCBs) quantitative
analysis. The experiments were carried out with a modified Varian SATURN III
quadrupole ion-storage mass spectrometer equipped with Varian waveform
generator, coupled with a gas chromatograph with DB-5 capillary column. The
disadvantage of using EI in the analysis of PCBs congeners is the extensive
fragmentation of the molecular ion. The main fragmentation pattern recorded in
the EI mass spectra of PCBs was the loss of a chlorine atom from the molecular
ion. Therefore the fragment-ion signal overlapped with the molecular-ion
cluster of lower mass congener. The fragmentation reactions of PCBs are
suppressed if methane is used as a reagent gas for chemical ionization, but
fragment ions are also present in the spectrum as an obstruction for
quantitative analysis. The most selective method for PCBs quantitative analysis
appears to be Cl with mass-selected C2H5+ ions from methane, which results in a mass spectrum with a
negligible amount of fragment ions.
Keywords: ion trap, mass spectrometry,
electron impact ionization, chemical ionization, selected ion chemical
ionization, polychlorinated biphenyls, Aroclor.
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J. Serb. Chem. Soc. 65(5-6)439-444(2000)
UDC 541.18.04/.045:539.194/.196
JSCS-2762
Original scientific paper
Separation of ions with the same charge
to mass ratio from a collision experiment
DRAGOLJUB S. BELIC and PIERRE DEFRANCE*
Faculty of Physics, P. O. Box 368,
YU-11000 Belgrade, Yugoslavia and
*Departement de Physique, Universite Catholique de Louvain, 2
Chemin du Cyclotron, B-1348, Louvain-La-Neuve, Belgium
(Received 27 October
1999, revised 24 February 2000)
Some atomic collision experiments lead to ions
having identical q/m ratio, as well as average velocity, so that standard
electric and magnetic analyzers are not able to identify them separately. This
situation occurs, for instance, in electron interaction with molecular
monocations (A2+) producing A22+ (direct ionization) and A+ (dissociation or
dissociative ionization). Due to the transfer of internal energy to the kinetic
energy of the fragments, they usually have a wider angular and energy
distribution in the laboratory frame, compared to direct ionization. By use of
a specially designed animated crossed beams apparatus, we are able to separate
ionization and dissociation fragments. Here the preliminary results of cross
sections measurements for electron impact on the nitrogen monocation, producing
N22+ and N+ ions, is reported
Keywords: ionization, dissociation, molecule,
monocation, mass analyzer, cross section, transmission efficiency.
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J.
Serb. Chem. Soc. 65(5-6)445-450(2000)
UDC 621.7:621.3.038.8
JSCS-2763
Original scientific paper
An attemp to use a pulsed CO2
laser for decontamination of radioactive metal surfaces
SCEPAN S. MILJANIC, NATASA N. STJEPANOVIC* and MILAN S. TRTICA*
Faculty of Physical Chemistry,
University of Belgrade, P. O. Box 137, YU-11001 Belgrade, and
*Vinca Institute of Nuclear Sciences, Department of Physical
Chemistry, P. O. Box 522, YU-11001 Belgrade, Yugoslavia
(Received 27 October
1999, revised 6 March 2000)
There is a growing interest in laser radioactive
decontamination of metal surfaces. It offers advantages over conventional
methods: improved safety, reduction of secondary waste, reduced waste volume,
acceptable cost. The main mechanism of cleaning by lasers is ablation. A pulsed
TEA CO2 laser was used in this work for surface cleaning in order to show
that ablation of metal surfaces is possible even at relatively low pulse
energies, and to suggest that it could be competitive with other lasers because
of much higher energy efficiencies. A brief theoretical analysis was made
before the experiments. The laser beam was focused using a KBr-lens onto a
surface contaminated with 137Cs (b-, t1/2 = 30.17 y). Three
different metals were used: stainless steel, copper and aluminium. The ablated
material was pumped out in an air atmosphere and transferred to a filter. The
presence of activity on the filter was shown by a germanium
detector-multichannel analyzer. The activity levels were measured by a GM
counter. The calculated decontamination factors and collection factors showed
that ablation occurs with a relatively high efficiency of decontamination. This
investigation suggests that decontamination using a CO2 laser should be
seriously considered.
Keywords: radioactivity, decontamination of
metals, CO2 laser, absorption of light, ablation, surface cleaning,
radioactive wastes.
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J.
Serb. Chem. Soc. 65(5-6)451-456(2000)
UDC 546.799.5:543.51
JSCS-2764
Original scientific paper
Determination of americium-241 in
sediments by gamma spectroscopy
MIRJANA DJ. RISTIC, SANDRO DEGETTO* and TEODOR AST
Faculty of Technology and
Metallurgy, Karnegijeva 4, Belgrade, Yugoslavia and
*Istituto di Chimica e Technologia del CNR, Corso Stati Uniti 4, I
35020 Padova, Italy
(Received 27 October
1999, revised 10 March 2000)
A radiochemical method is given for the
determination of Am-241 from the global fallout in sediments. The concept of a
concentration step to separate Am-241 from the bulk of the sample (1-2 kg wet)
by coprecipitation followed by low energy gamma spectroscopy was investigated.
A series of experiments with tracer added was performed to measure the recovery
of americium by coprecipitation. Also, a number of real samples without tracer
were examined and the conditions for the optimum separation are given. The
applied gamma method and the conventional, accurate, but tedious, aplha
technique via 243Am, which is usually applied for the
determination of Am-241, agreed mostly within 10 %.
Keywords: americium-241, low energy gamma
spectroscopy, sediments, preconcentration.
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article click here (284 KB WinZip file)
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Last
Updated June 21, 2000.
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more information contact: SHD@elab.tmf.bg.ac.yu