
Vinijchuk, A. V.; Golovina, N. A.; Polishchuk, A. P.; Puchkovskaya, G.
In this report IR spectra of cholesteryle naloxybenzoates homologes (n=1, 36, 110, 16) in 100570 K temperature range have been studied and Xray structural analysis of the crystals has been performed. On the base of interpreted spectra the IRband, which are the most sensitive to phase transitions, were found. These are the esteric group vibrations $(11001120 cm^{1}, 12401290 cm^{1}, 17001740 cm^{1})$ 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 nalkaonates of cholesterine, the methylene chains of all investigated homologues are melted in crystalline phase even...

Puchkovskaya, G.; Barabash, Alexander; Gavrilko, T.; Baran, J.; Ratajczak, H.
Ferroelectric $\alphakIO_{3} \cdot HIO_{3} (T_{c} = 223k)$ 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 lowtemperature ferroelectric phase and the dynamics of phase transition the temperature variable FT  IR study $(4000400 cm^{1})$ of polycrystalline $\alphaKIO_{3} \cdot HIO_{3}$ 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...

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 halfwidths 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 orderdisorder character. Quantitative analysis of the spectra according to lattice dynamics theories and using $^{127}I$...

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 singletsinglet 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...

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 absorptionemission 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 cutoff might be due to a competition between vertical Rydberg excitations and the adiabatic ionization limit. To observe infinite Rydberg series, we performed...

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.

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.

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...

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....

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 665720nm. 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 nonradiative 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...

Sharma, R. C.; Thakur, S. N.; Kundu, T.
Two photon optogalvanic trasitions in Ar glow discharge with NdYAG laser pumped tunable dye laser excitation in the frequency range $1651513520 cm^{1}$ 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...

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 wavelengthselected fluorescence excitation (WSFE) spectra of YCl have been studied. The electronic transitions $B^{1}\PiX^{1}\sum^{+}, C^{1}\sum^{+}  X^{1}\sum^{+}, D^{1}\Pi  X^{1}\sum^{+}, D^{1}\PiA^{1}\Delta, J^{1}\Pi X^{1}\sum^{+}, K^{1}\Pi  X^{1}\sum^{+}d^{3}\Phi  a^{3}\Delta$ and $g^{3}\Delta  a^{3}\Delta$ have been rotationally analyzed. The $X^{1}\sum^{+}  a^{3}\Delta$ energy separation has also...

Luque, Jorge; Crosley, David R.
New band intensity ratios have been measured for the OH(AX), CH(AX), and CH(BX) 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 rcentroid approximation. Weak offdiagonal 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...

Mellinger, A.; Vidal, C. R.
Triplet Rydberg series of Carbon Monoxide in the range of n=49 have been rotationally analysed for the first time using a threestep excitation scheme. The $X^{1}\sum^{+} \rightarrow a^{\prime}3\sum^{+} (014)$ intercombination transition was pumped with tunable, coherent VUV radiation generated in Mg vapour by fourwave mixing. With two subsequent spinallowed 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 laserreduced fluorescenc allows the study of strongly...

Dupré, Patrick; Zhang, Q.; Vaccaro, P. H.
Internally cold samples of the transient $S_{2}O$ molecule are produced in a supersonic freejet expansion and interrogated through the use of Degenerate FourWave Mixing (DFWM) spectroscopy. The enormous resonant enhancement inherent to this nonlinear optical technique provides an ``absorptionbased'' detection scheme which can approach the trace species sensitivity afforded by conventional LaserInduced 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 nearcomplete resolution of the corresponding rotational structure. The DFWM results are compared with data derived from simultaneous LIF measurements and are simulated through...

Zhang, Q.; Dupré, Patrick; Grzybowski, B.; Vaccaro, P. H.
Laserinduced 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 $S_{2}O$ (315340nm) under supersonic freejet conditions that yield effective rotational temperatures of roughly 1 K. Least squares analysis of highresolution scans performed on the ${2^{\nu}}_{0}(\nu = 0  5)$ progression, where $\nu_{2}$ corresponds to the $SS$ 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 $SS$ stretching...

Delgado, R.; Matos, K.; Chen, X. L.; Hossenlopp, J.; Weiner, B. R.
Thionylaniline (PhN=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 BX 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 440520 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...

Kanamori, Hideto; Tanigawa, Kouichi
A triplet state of acetylene was generated by pulsed mercury photosensitized 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 ctype 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 cisbend. 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...

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 IFS120HR) or a 1.0m 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...

Selco, J. I.; Carrick, P. G.
Jet cooled electronic emission spectra from ortho, meta, and paraxylyl (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 paraxylyl 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...