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#### The KnowledgeBank at OSU (75.279 recursos)

Knowledge Bank contains collections of presentations, publications and reports related to Ohio State University.

Abstracts of OSU International Symposium on Molecular Spectroscopy 1990-1999

1. #### CONFORMATIONAL MOBILITY OF CHOLESTERYLE n-ALKOXYBENZOATES AT THE PHASE TRANSITIONS

Vinijchuk, A. V.; Golovina, N. A.; Polishchuk, A. P.; Puchkovskaya, G.
In this report IR spectra of cholesteryle n-aloxybenzoates homologes (n=1, 3-6, 110, 16) in 100-570 K temperature range have been studied and X-ray structural analysis of the crystals has been performed. On the base of interpreted spectra the IR-band, which are the most sensitive to phase transitions, were found. These are the esteric group vibrations $(1100-1120 cm^{-1}, 1240-1290 cm^{-1}, 1700-1740 cm^{-1})$ and the benezene ring stretching vibrations Q (C = C) $(1515 cm^{-1}, 1580 cm^{-1}, 1610 cm^{-1})$, It was found that in contrast to n-alkaonates of cholesterine, the methylene chains of all investigated homologues are melted in crystalline phase even...

2. #### FT-IR AND NQR STUDIES OF PHASE TRANSTION IN $\alpha-KIO_{3}$ CRYSTAL

Puchkovskaya, G.; Barabash, Alexander; Gavrilko, T.; Baran, J.; Ratajczak, H.
Ferroelectric $\alpha-kIO_{3} \cdot HIO_{3} (T_{c} = 223k)$ at T = 300k belongs to monoclinic $syngony^{1}$ (space group $p21/c, z = 4$) and consists of two sets of dimers $H(Io3)2^{-}$, connected by strong $(R_{O\ldots O} = 2, 5A)$ hydrogen bonds. In order to clarify the structure of low-temperature ferroelectric phase and the dynamics of phase transition the temperature variable FT - IR study $(4000-400 cm^{-1})$ of polycrystalline $\alpha-KIO_{3} \cdot HIO_{3}$ have been performed from T = 300 to 13k. Pressure dependable NQR measurements (0 - 5kbar) have been performed $earlier^{2}$ at T=300 and 77K. On cooling to low temperatures the ABC...

3. #### TEMPERATURE VARIABLE LOW-FREQUENCY RAMAN SPECTRA AND ORIENTATION DISORDER IN $NH_{4}IO_{3}$ CRYSTAL

Barabash, Alexander; Gavrilko, T.; Sekirin, I. V.
The ammonium iodate $NH_{4}IO_{3}$ crystal is $known^{1}$ as ferroelectric with displacing type phase transition $(T_{c} = 367K)$, Polarized temperature variable lowfrequency Raman scattering $(W < 200 cm^{-1})$ studies in the phase transition region are presented. Measurements of peak positions of external'' rotational and translation optical modes and their half-widths allow to detect the orientation disorder and help to determine its character as well as a mechanism of the phase transition to the ordered phase. It appeared to be continuous and of the mixed displacing and order-disorder character. Quantitative analysis of the spectra according to lattice dynamics theories and using $^{127}I$...

4. #### SPECTROSCOPY OF $C_{60}$ IN RARE GAS MATRICES

Zerza, G.; Sassara, A.; Chergui, M.
Taking advantage of matrix isolation (i.e. high density of species, low density of states, hindered rotations), we have carried out a spectroscopic study of $C_{60}$ in rare gas matrices as well as in pure $C_{60}$ films at low temperature. Absorption (in the range of 420 to 750 nm), emission and excitation spectra for excitation in the range of 550 to 650 nm have been obtained. Orbitally forbidden singlet-singlet transitions are observed between 480 and 650 nm in accord with absorption spectra of $C_{60}$ in solution but with a better resolution and different matrix shifts. This last effect can be explained...

5. #### Rydberg-Rydberg molecular transitions in the condensed phase: towards the ionisation limit

Zerza, G.; Sassara, A.; Stepanenko, V.; Vigliotti, F.; Chergui, M.
The Rydberg states of NO in rare gas matrices show a strong interaction with the surrounding, expressed by shifts to higher energies with respect to the gas phase of up to 1 eV, large absorption-emission Stokes shifts due to extensive cage relaxation and drastic lengthening of the lifetimes. Up to now absorption measurements from the ground state have shown Rydberg series up to n=4 in Ne and n=3 in the other matrices. It was suspected that the cut-off might be due to a competition between vertical Rydberg excitations and the adiabatic ionization limit. To observe infinite Rydberg series, we performed...

6. #### LASER INDUCED EMISSION FROM NFC1 RADICALS ISOLATED IN LOW TEMPERATURE ARGON MATRICES

Gilbert, Julanna V.; Okin, Greg S.
The spectrum and lifetime of laser induced emission from NFCl radicals isolated in low temperature argon matrices is reported. The spectrum is compared to emission observed following the photolysis of gas phase $NFCl_{2}$, and the tentative assignment of the gas phase emission to NFCl is $confirmed.^{1}$ The lifetime of the NFCl emission in the matrix is $610\pm40$ ns. A mechanism involving the ability of different vibrational modes of predissociated electronic states to couple in the low temperature matrix environment is discussed, and used to explain the difference in lifetimes observed for the gas phase and the matrix emission.

7. #### Photoinduced Reaction Pathways of HCl Dimers in an Argon Matrix

Lawrence, W. G.; Lin, H.- S.; Goedderz, K. H.; Heaven, M. C.
The photoinduced reaction of HCl dimers upon 193 nm excitation is demonstrated by the formation of $Cl_{2}$ monomers. The products were detected by laser induced fluorescence from the $Cl_{2}A^{\prime} \rightarrow X$ transition. Two mechanisms for the formation of $Cl_{2}$ are considered. The first requires two sequential H atom cage exit steps. Alternatively, a single step mechanism for the caged reaction is considered. A statistical model for deriving the rate constant of the caged reaction will be presented.

8. #### THE VIBRATIONAL SPECTRUM OF $BF_{2}OH$ TRAPPED IN SOLID NEON

Irikura, K. K.; Jacox, Marilyn E.; Thompson, Warren E.
Although the interaction of $BF_{3}$ with traces of water in the vacuum system has been $shown^{1}$ to result in the formation of sufficient $BF_{2}OH$ for determination of its microwave spectrum and structure, the infrared spectrum of that molecule has not previously been reported. Prominent impurity absorptions in the infrared spectra of solid $Ne:BF_{3}$ samples at 5 K can be assigned to $BF_{2}OH$, formed by the reaction of $BF_{3}$ with water adsorbed on the walls of the deposition system. This assignment is supported by the results of experiments in which the sampling system is exposed to water enriched in deuterium and/or...

9. #### ANALYSIS OF THE FREQUENCY SHIFTS IN IR SPECTRA OF CO ADSORBED ON THE $Na_{4} Ca_{4}$ A ZEOLITE

Larin, A. V.
The zeolite $Na_{4} Ca_{4}$ A models are found via a fitting of vibrational frequency shift and a band splitting in IR spectra of $H_{2}$ adsorbed on the same zeolite. The different models distinguish in the oxygen charges of the different crystallographic sites, charge of Cation. Two peak positions are found in accordance with experimental CO spectra. The peak position changes are discussed due to an effective molecular size variations for the models found. The respective comparison will be presented. Appications to CO molecule of a simplified method of the frequency shift calculation1 earily proposed for $H_{2}$ molecule will be given....

10. #### LASER PHOTOACOUSTIC SPECTROSCOPY OF $Br_{2}$ VAPOUR IN THE EXTREME RED REGION $(13800-15000 Cm^{-1})$

Sharma, R. C.; Thakur, S. N.
Electronic bands belonging to the $A{^{3}\Pi_{1u}} \leftarrow X^{1}{\sum^{+}}_{g}$ transitions in the $Br_{2}$ vapour have been recorded photoacoustically in the wave length region 665-720nm. The vibronic levels involved in these trasitions are $3 \leq v^{\ast} \leq 2l$ and relative photoacoustic band intensities have been used in estimating the non-radiative relaxation rates from upper vibronic levels of $A{^{3}\Pi_{1u}}$ state. The nonradiative rate constant is found to be a nonfinear function of the upper state vibrational quantum number. A comparison of the calculated radiative rate constants as a function of excited $A{^{3}\Pi_{1u}}$ state vibronic levels does not quite reflect the expected complementry behavior...

11. #### LASER OPTOGALVANIC SPECTROSCOPY OF Fe-Ar HOLLOW CATHODE LAMP IN WAVELENGTH REGION 605-740nm

Sharma, R. C.; Thakur, S. N.; Kundu, T.
Two photon optogalvanic trasitions in Ar glow discharge with Nd-YAG laser pumped tunable dye laser excitation in the frequency range $16515-13520 cm^{-1}$ has been studied using linearly and circularly polarization radiation. The metastable $4s[3/2]^{0}2$ level accounts for more than half of the 38 two photon resonant transitions whereas 10 of them originate in $4s[3/2]^{O}1$ four in $4s^{\prime}[1/2]^{O}0$ and only two in $4s^{\prime}[1/2]^{O}1$ level. The intensities of two photon optogalvanic transitions are very sensitive to changes in the incident laser power which is not the case with one photon transitions. Intensity ratios for circular to linear polarization for two photon transitions...

12. #### HIGH RESOLUTION SPECTROSCOPY OF YCl AND LaCl

Xin, J.; Edvinsson, G.; Klynning, L.; Royen, P.
The group III transition metal monochlorides, YCl and Lacl, have been experimentally investigated by means of high resolution grating spectroscopy, Fourier transform spectroscopy, and various laser spectroscopic techniques. A complete survey on the spectrum of YCl has been carried out. Thermal emission, the emission from a dc discharge tube, the absorption, laser induced fluorescence (LIF) and wavelength-selected fluorescence excitation (WSFE) spectra of YCl have been studied. The electronic transitions $B^{1}\Pi-X^{1}\sum^{+}, C^{1}\sum^{+} - X^{1}\sum^{+}, D^{1}\Pi - X^{1}\sum^{+}, D^{1}\Pi-A^{1}\Delta, J^{1}\Pi- X^{1}\sum^{+}, K^{1}\Pi - X^{1}\sum^{+}d^{3}\Phi - a^{3}\Delta$ and $g^{3}\Delta - a^{3}\Delta$ have been rotationally analyzed. The $X^{1}\sum^{+} - a^{3}\Delta$ energy separation has also...

13. #### EXPERIMENTAL DETERMINATION OF ELECTRONIC TRANSITION MOMENTS IN HYDRIDES: OH(A-X), CH(A-X), AND CH(B-X)

Luque, Jorge; Crosley, David R.
New band intensity ratios have been measured for the OH(A-X), CH(A-X), and CH(B-X) band systems, using laserinduced fluorescence in low pressure flames. We use these ratios to directly fit electronic transition moments for each system expressed in polynomial form, without recourse to the r-centroid approximation. Weak off-diagonal bands are included in the fit. This provides a new degree of accuracy in the transition moments, and has been used to calculate absorption and emission coefficients. The results will be compared with ab initio moments, and applications to determination of rotational temperatures and absolute concentrations of CH using both band systems will...

14. #### Triplet Rydberg Series of Carbon Monoxide

Mellinger, A.; Vidal, C. R.
Triplet Rydberg series of Carbon Monoxide in the range of n=4-9 have been rotationally analysed for the first time using a threestep excitation scheme. The $X^{1}\sum^{+} \rightarrow a^{\prime}3\sum^{+} (0-14)$ intercombination transition was pumped with tunable, coherent VUV radiation generated in Mg vapour by four-wave mixing. With two subsequent spin-allowed steps (see figure) at visible wavelengths via the $c^{3}\Pi$ state, the energy region between 105 400 and $112 500 cm^{-1}$ was probed. While scanning the wavelength of the third step, the fluorescence $c^{3}\Pi \rightarrow a^{3}\Pi(0 \rightarrow v^{\prime\prime})$ was monitored. This detection scheme based on laser-reduced fluorescenc allows the study of strongly...

15. #### HIGH-RESOLUTION NONLINEAR SPECTROSCOPY OF TRANSIENT POLYATOMIC SPECIES: DEGENERATE FOUR-WAVE MIXING STUDIES OF JET-COOLED $S_{2}O$ IN THE VICINITY OF A PREDISSOCIATION LIMIT

Dupré, Patrick; Zhang, Q.; Vaccaro, P. H.
Internally cold samples of the transient $S_{2}O$ molecule are produced in a supersonic free-jet expansion and interrogated through the use of Degenerate Four-Wave Mixing (DFWM) spectroscopy. The enormous resonant enhancement inherent to this nonlinear optical technique provides an absorption-based'' detection scheme which can approach the trace species sensitivity afforded by conventional Laser-Induced Fluorescence (LIF) probes. The ${2^{3}}_{0}$ and ${2^{4}}_{0}$ vibronic bands of the intense $S_{2}O \tilde{C}^{1}A^{\prime} - \tilde{X}^{1}A^{\prime} (\pi^{\ast} \leftarrow \pi)$ transition $(\sim30900 cm^{-1})$ are examined with near-complete resolution of the corresponding rotational structure. The DFWM results are compared with data derived from simultaneous LIF measurements and are simulated through...

16. #### LASER-INDUCED FLUORESCENCE STUDIES OF JET-COOLED $S_{2}O$: AXIS-SWITCHING AND PREDISSOCIATION EFFECTS

Zhang, Q.; Dupré, Patrick; Grzybowski, B.; Vaccaro, P. H.
Laser-induced fluorescence spectroscopy has been used to probe the intense $\tilde{C}A^{\prime} - \tilde{X}^{1}A^{\prime}(\pi^{\ast} \leftarrow \pi)$ electronic system of $S_{2}O$ (315-340nm) under supersonic free-jet conditions that yield effective rotational temperatures of roughly 1 K. Least squares analysis of high-resolution scans performed on the ${2^{\nu}}_{0}(\nu = 0 - 5)$ progression, where $\nu_{2}$ corresponds to the $S-S$ stretching mode, not only furnish refined band origins and rotational constants, but also provide evidence for an axis switching effect in this asymmetric triatomic species. Based on the limited set of vibronic bands examined in the present study, the harmonic frequency and anharmonicity for $S-S$ stretching...

17. #### THE LASER SPECTROSCOPY OF DEHYDROAZEPINE

Delgado, R.; Matos, K.; Chen, X. L.; Hossenlopp, J.; Weiner, B. R.
Thionylaniline (Ph-N=S=O) is photodissociated at 193 and 248 nm, to produce ground state SO $(X^{3}\sum^{-})$ The nascent vibrational state distribution of the SO $(X^{3}\sum^{-})$ radical is observed by laser induced fluorescence (LIF) on the B-X transition. The vibrational state distribution of the SO photofragment provides insight into the cleavage of the N=S bond of thionylaniline. A gas phase LIF excitation spectrum of a transient species in the region of 440-520 nm is also obtained following the same photodissociation. The carrier of this spectrum is attributed to dehydroazepine, based on kinetic and chemical reactivity studies. This hypothesis is further confirmed by...

18. #### High-Resolution Study of the Triplet Acetylene

Kanamori, Hideto; Tanigawa, Kouichi
A triplet state of acetylene was generated by pulsed mercury photo-sensitized technique and was detected by using near infrared diode laser kinetic spectroscopy. Hundreds of lines were observed in Doppler limited resolution and were assigned to the c-type electronic transition of a triplet asymmetric rotor. The intensity alternation due to two equivalent protons appeared in the asymmetry (K-)doubling clearly showed that the structure of the triplet acetylene is cis-bend. The band origin and rotational constants agrees well to low resolution $spectra^{1})$ and theoretical results of the acetylene in the triplet states, respectively. A same results were also obtained in the...

19. #### OBSERVATION OF HIGH RESOLUTION EMISSION SPECTRA OF BENZYL AND XYLYL RADICALS IN THE VISIBLE RANGE.

Lee, Sang K.; Choi, Iek Soon
We have built the spectrometer for obtaining a high resolution enission spectra of unstable species in the visible and u.v. range. For the spectrometer, a high resolution Fourier transform spectrometer (Bruker IFS-120HR) or a 1.0-m path length of monochromator has been employed with a PMT detector. The unstable species was generated in a Jet by an electric DC discharge in a supersonic expansion chamber made by a Pyrex glass tube. With this facility, we have obtained the high resolution emission spectra of benzyl and xylyl radicals generated from toluene and xylenes, respectively. The spectra show good S/N and the rotational...

20. #### JET COOLED EMISSION SPECTRA OF THE XYLYL RADICALS

Selco, J. I.; Carrick, P. G.
Jet cooled electronic emission spectra from ortho, meta, and para-xylyl (methylbenzyl) radicals have been recorded using a corona excited supersonic expansion (CESE) apparatus. A full vibronic analysis of the $D_{1} \rightarrow D_{0}$ transitions for all three isomers has been carried out allowing for unambiguous assignments of the gas phase ground state vibrational frequencies. Based on band contours observed for the para-xylyl radical, the band at $458.3 cm^{-1}$ is reassigned to the 6b vibration instead of the 6a vibration. For the vibrational modes exhibiting progressions, anharmonicity constants are calculated. Temperatures of approximately 15 K were attained. Although CESE excitation of the...

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