Showing papers on "Hot band published in 1989"
01 Dec 1989
TL;DR: In this article, a complete survey of the rovibrational spectrum of gaseous hydrogen fluoride and its D-isotopomers under equilibrium conditions from the far infrared (low-frequency fundamentals of (HF)2) to the visible (N=4 overtones of the HF stretching vibrations in (HF n) by interferometric Fourier transform spectroscopy is presented.
Abstract: We have measured a complete survey of the rovibrational spectrum of gaseous hydrogen fluoride and its D-isotopomers under equilibrium conditions from the far infrared (low-frequency fundamentals of (HF)2) to the visible (N=4 overtones of the HF stretching vibrations in (HF)n) by interferometric Fourier transform spectroscopy. The data have been analyzed in terms of the tunneling splittings for the hydrogen bond rearrangements (H(1)-F...H(2)-F)⇄(F-H(1)...F-H(2)), which are highly mode specific. Furthermore, narrow line structure is observed for the HFstretching fundamentals and overtones in (HF)2 from N=1 to N=4. These are found to be inconsistent with quasi-equilibrium (RRKM) theories of unimolecular dissociation. Simplified coupled channel calculations by Halberstadt et al. predict lifetimes that are reasonably consistent with experiment. The results are discussed in terms of an adiabatic separation of the two high-frequency HF stretching modes and the four low-frequency modes in (HF)2.
115 citations
TL;DR: In this paper, a corona excited supersonic expansion was used to obtain a rotationally cooled gas-phase electronic emission spectra of toluene and the benzyl radical.
98 citations
TL;DR: In this article, the results of a harmonic vibrational analysis within the AM1 method for the C60 and C70 clusters are presented (for the latter cluster this is the first vibrational information available).
Abstract: The results of a harmonic vibrational analysis within the AM1 method for the C60 and C70 clusters are presented (for the latter cluster this is the first vibrational information available). The harmonic frequencies of the 378 vibrational modes lie in the range 237–1862 cm−1. The results, which represent the largest systems for which vibrational analysis has so far been carried out on a quantum-chemical basis, are used to illustrate some aspects of the application of conventional quantum-chemical vibrational analysis to giant molecular systems.
85 citations
TL;DR: In this paper, the properties of the vibrational modes, their symmetries and relationship to the modes of the bulk components are discussed, as well as the relationship between these modes and those of their bulk components.
74 citations
TL;DR: In this article, the spectrum of the linear carbon chain molecule C5 in the gas phase has been studied around 2170 cm−1, the region of the highest asymmetric stretching vibration ν3.
Abstract: The spectrum of the linear carbon chain molecule C5 in the gas phase has been studied around 2170 cm−1, the region of the highest asymmetric stretching vibration ν3. The results were obtained using a tunable diode laser spectrometer and a cooled hollow cathode discharge in a flowing mixture of acetylene and helium. Four vibration–rotation bands were assigned and analyzed: the fundamental, a hot band arising from the v7=1, l=1 vibrational level, a second hot band arising from v7=2, l=0, and a third hot band tentatively ascribed to v5=1, l5=1. Small local perturbations were found to affect the upper vibrational states of two of the bands. Analysis of the data yielded accurate values for a number of molecular parameters for C5, e.g., the band origin ν3= 2169.4410(2) cm−1, the rotational constant, B0 =2557.63(9) MHz, and the l‐type doubling parameters, q7=3.99(6) MHz, and q5=2.36(9) MHz. The value of q7 may be used to estimate a value of 118 cm−1 for the lowest bending frequency of the molecule. There is no e...
73 citations
TL;DR: In this paper, a vibrational Hamiltonian is proposed for regions containing overtones or combinations of the three normal modes, excluding the symmetric inversion motion, which is capable of modeling the normal mode to local mode transition observed in the spectrum as well as the observed band origins, rotational constants and intensifies.
65 citations
TL;DR: In this paper, a diode laser spectroscopic method was used to detect the C3 molecule produced by the photolysis of allene or by the discharge in cyclopropane or furan.
Abstract: The ν3 hot bands (011)–(010), (021)–(020), and the combination band (021)–(000) of C3 were observed by a diode laser spectroscopic method. The C3 molecule was produced by the photolysis of allene or by the discharge in cyclopropane or furan. Analysis gave molecular constants in each vibrational state and also the energy difference between (020) and (000). The derived vibrational frequencies were compared with the result of a Morse oscillator‐rigid bender internal dynamics (MORBID) calculation by Jensen.
57 citations
54 citations
TL;DR: In this paper, the H-F stretching bands of the OCO-HF and SCO-HF complexes have been studied by optothermal (bolometer-detected) molecular-beam spectroscopy.
Abstract: The H–F stretching bands of the OCO–HF and SCO–HF complexes have been studied by optothermal (bolometer‐detected) molecular‐beam spectroscopy. Both species exhibit spectra of a quasilinear molecule red shifted from free HF by 52.1 and 57.5 cm−1, respectively. The principal band in both molecules is accompanied by a slightly red‐shifted doublet‐type subsidiary band that can be interpreted as a hot band of a low frequency bending vibration or a K=1 subband of a bent molecule. Accurate doublet splittings in the ground H–F vibrational state have been measured by pulsed‐nozzle Fourier‐transform microwave spectroscopy.
44 citations
TL;DR: In this paper, S1 trans-stilbene (tSB) in a jet, particularly those for fundamental vibrational levels above the isomerization barrier, are reported with three partially isotope-substituted analogues.
Abstract: Vibrational mode assignments of S1 trans‐stilbene (tSB) in a jet, particularly those for fundamental vibrational levels above the isomerization barrier, are reported with three partially isotope‐substituted analogues (C6 H5 –13CH=13CH–C6 H5 , C6 H5 –CD=CD–C6 H5 , and C6 D5 –CH=CH–C6 D5 ). Vibrational levels are assigned on the basis of the frequency shifts due to isotopic substitution. The established mode assignments then enable us to discuss the individual band intensities in the fluorescence excitation spectra which bear mode specific information on the isomerization dynamics in isolated tSB molecules. Upon deuteration, the intensities of several CH deformation modes increase drastically as their frequencies become lower than the isomerization barrier. Intensities of several fundamental bands are found much smaller than those of nearby combination bands, contrary to what is expected from ordinary absorption spectra in condensed phases. The intensity ratio of the 71 (C=C stretch) to the 00 band is semiq...
44 citations
TL;DR: In this article, the Renner-Teller effect in the bending vibrational mode of this radical was investigated for both the X2(Π) and A(2π) states.
Abstract: Laser‐induced fluorescence excitation spectra have been recorded for many vibronic transitions of the A(2Π)–X(2Π) and B(2Σ+)–X(2Π) systems of NCS under supersonic free jet expansion conditions. New assignments have been made for many of these bands and several of the assignments from previous work have been revised. Vibronic energies have been determined for levels involving excitation of all three vibrational modes in the ground electronic state and both excited electronic states. A detailed rotational and vibrational analysis has been carried out for levels involving excitations of the two stretching modes and the many rotational and potential function constants have been determined for the A and X states. The variation of the spin–orbit constant with vibrational level has also been investigated. Results of this paper provide the ground work for a detailed analysis of the Renner–Teller effect in the bending vibrational mode of this radical for both the X2(Π) and A(2Π) states to appear in a forthcoming p...
TL;DR: In this paper, the infrared spectrum of gaseous CH3I has been investigated in the range 500-16'500 cm−1, up to six quanta of excitation in CH stretching.
Abstract: The infrared spectrum of gaseous CH3I has been investigated in the range 500–16 500 cm−1, up to six quanta of excitation in CH stretching. A total of 16 perpendicular bands lying above 3700 cm−1 have been analyzed, some as Fermi resonance diads, in order to determine accurate vibrational wave numbers for the constituent levels. The local mode model has been applied to the CH stretching manifold to account for anharmonicity and the effects of Darling–Dennison resonances. Vibrations not involving CH stretching have been treated in a normal mode basis. The joint approach, which also takes into account known Fermi resonances, enables a complete set of 27 vibrational anharmonicity parameters to be determined for CH3I which fits 63 observed vibrational levels up to V=6 with a root‐mean square (rms) error of 2.75 cm−1.
15 Nov 1989
TL;DR: In this article, the isotopic dependence of vibration-rotation constants of the HeH{sup +} molecular ion has been studied using infrared spectra of the hot band of the ion.
Abstract: Isotopic species of the HeH{sup +} molecular ion provide an excellent testing ground for studying isotopic dependence of vibration--rotation constants because of the small masses of He and H isotopes. We have observed infrared spectra of the hot band {ital v}=2{l arrow}1 of HeH{sup +} and fundamental bands of isotopic species HeD{sup +}, {sup 3}HeH{sup +}, and {sup 3}HeD{sup +}, and obtained the Dunham coefficients {ital Y}{sub {ital kl}}, and the isotopically independent parameters {ital U}{sub {ital kl}}, {Delta}{sup He}{sub {ital kl}}, and {Delta}{sup H}{sub {ital kl}}.
TL;DR: In this paper, the authors performed ultrafast laser experiments on low temperature crystals of pentacene in naphthalene (PTC/N) to study the process of vibrational cooling.
Abstract: Ultrafast laser experiments are conducted on low temperature crystals of pentacene in naphthalene (PTC/N) to study the process of vibrational cooling. A vibration of the excited singlet state, denoted Sν1, is excited, and the decay out of this state, as well as the subsequent arrival at the vibrationless ground state S01, are monitored by photon echoes, absorption recovery, and a new technique, pump‐induced coherent Stokes Raman scattering [T.‐C. Chang and D. D. Dlott, Chem. Phys. Lett. 147, 18 (1988)]. Eight vibrational modes of PTC, ranging from 260 to 1350 cm−1 are studied. The experimental results are interpreted using a previously developed model of vibrational cooling [J. R. Hill and D. D. Dlott, J. Chem. Phys. 89, 830 (1988)]. This model predicts the dependence of the vibrational cooling rate on the amount of excess vibrational energy and the temperature. The motion of the vibrational probability distribution toward the ground state is predicted to occur with a temperature independent ‘‘vibrational...
TL;DR: In this article, the infrared laser absorption spectra of an ac discharge using velocity modulation detection were used to derive rotation, spin-rotation, and distortion parameters for the ground state and the first two vibrationally excited states of the bending mode.
Abstract: Infrared laser absorption spectra of H2O+ have been recorded in an ac discharge using velocity modulation detection. Eighty‐five lines of the 210 fundamental and 20 lines of the 221 hot band were used to derive rotation, spin‐rotation, and distortion parameters for the ground state and the first two vibrationally excited states of the bending mode. The results are compared with those from analysis of the A–X band system and from rotational and vibration–rotation laser spectra, as well as with recent ab initio results obtained using MRCI wave functions.
TL;DR: In this paper, the authors used the optothermal molecular beam technique to record the near infrared spectrum of the acetylene-HF binary complex associated with the ν7 vibrational mode (asymmetric C-H stretch).
Abstract: The optothermal molecular beam technique has been used to record the near infrared spectrum of the acetylene–HF binary complex associated with the ν7 vibrational mode (asymmetric C–H stretch). A fit to this perpendicular band spectrum gives accurate rotational constants for both the ground and excited vibrational states, as well as the vibrational origin, namely A‘=1.192 60(5) cm−1 , B‘=0.157 34(1) cm−1 , C‘=0.138 10(1) cm−1 , A’=1.186 90(5) cm−1 , B’=0.157 34(1) cm−1 , C’=0.138 08(1) cm−1, and ν0 =3276.2889(30) cm−1 . From the homogeneous linewidths of the observed transitions the lifetime of the excited vibrational state has been determined to be 3.6 ns. When compared with the lifetime determined previously for the ν1 mode (0.8 ns) and the data obtained previously for several other systems, it is clear that vibrational relaxation in this molecule is mode specific. A discussion is given concerning the nature of this relaxation process.
TL;DR: In this paper, the gas-phase infrared spectrum of two isotopic forms of thallium hydride (TlH 70.5% and 203 TlH 29.5%) in their ground electronic states has been observed using a diode laser spectrometer.
TL;DR: In this article, the potential energy surface calculated for H3+ by Meyer, Botschwina, and Burton was used to calculate the frequency of the (v = 2 - v = 1) and (v − v = 2) transitions from lower states with one quantum of vibrational energy to upper states with two vibrational quanta.
TL;DR: In this article, the authors investigated Raman excitation profiles and resonance Raman spectral lines of polyatomic molecules strongly coupled to a continuum of environmental nuclear modes, and the solvent effects are regarded as dynamic and homogeneous and the approach rests on vibrational density matrices including both molecular and solvent modes in the ground and excited electronic states.
TL;DR: In this article, the analysis of high-resolution absorption spectra of the A-X band system in C 2 D 2 leads to assignment of 130 out of 135 bands observed between 41 500 and 47 900 cm −1.
TL;DR: In this paper, the infrared spectrum of gas-phase GaH in its ground electronic state has been observed using a diode laser spectrometer, and a total of 113 transitions with a nominal accuracy of ± 0.001 cm−1.
TL;DR: In this article, the authors investigated the quanta quanta produced in the bath of CO2 and N2O using a continuous wave IR diode laser and found that less than 20% of the energy initially placed in the NO2 by the dye laser is taken up by the vibrational degrees of freedom of the CO2 or N2 O baths.
Abstract: Quenching of highly excited vibrational states of NO2 in baths of CO2 and N2O has been investigated. Dilute NO2 mixtures were excited by a pulse from an excimer pumped dye laser operating at 495 nm. Various vibrational modes of the bath gases were probed with continuous wave IR diode lasers. Less than 20% of the energy initially placed in the NO2 by the dye laser is taken up by the vibrational degrees of freedom of the CO2 or N2O baths. For N2O, the three different vibrational modes (ν1=1285 cm−1, ν2=589 cm−1, ν3=2223 cm−1) take up almost equal amounts of energy from NO2, but the number of vibrational quanta produced in the bath is found to increase with decreasing vibrational frequency. Similar results are found for CO2 except that the ν1 and ν2 modes cannot be studied separately for this bath gas due to rapid ν1↔ν2 intermode equilibration.
TL;DR: In this article, the absolute integrated band intensities (S{sub v}{sup 0}) for the {nu}{sub 1} fundamental bands of HN{sub 2} and HCO{sup +} were determined by the recently developed technique of direct laser absorption spectroscopy in fast ion beams.
Abstract: The authors report the determination of absolute integrated band intensities (S{sub v}{sup 0}) for the {nu}{sub 1} fundamental bands of HN{sub 2}{sup +} and HCO{sup +} by the recently developed technique of direct laser absorption spectroscopy in fast ion beams. The values obtained for HN{sub 2}{sup +} (1,250 (300) cm{sup {minus}2} atm{sup {minus}1}) and HCO{sup +} (430 (100) cm{sup {minus}2} atm{sup {minus}1}) are substantially lower than corresponding results from high level ab initio calculations.
TL;DR: In this article, an accurate two-mode model of HCN is used to demonstrate a technique for and the utility of using optimized linear combinations of bond modes to describe molecular vibrational states.
Abstract: An accurate two mode model of HCN is used to demonstrate a technique for and the utility of using optimized linear combinations of bond modes to describe molecular vibrational states. While normal modes are exact at zero energy and bond modes describe dissociations conveniently, neither set of coordinates describe accurately the motions of most of the spectroscopically accessible molecular vibrational states of HCN. We present a newly developed method of describing molecular vibrations with an optimized set of linear combinations of bond modes. The Hamiltonian is canonically transformed to these coordinates using the transformation method. Subsequent diagonalization of the rotated Hamiltonian matrix gives the unaltered energies and a much improved description of the molecular vibrations as measured by the projection of the eigenstates onto the zero order states. This technique improves spectroscopic assignments and simplifies visualization of the quantum vibrational motions of molecules. This is illustrated by resolving an apparent intensity anomaly in the overtone spectrum of HCN.
TL;DR: The infrared diode laser spectrum of the SiF + ion generated in a SiF 4 plasma has been observed in this article, where a sharp decrease of the intensity caused by the magnetic field, which is characteristic of ion lines, was observed.
TL;DR: In this paper, the laser-induced fluorescence (LIF) excitation spectrum of the A 2A1 ← X 2E band system of the CH3O radical has been studied at both low (≈ 10 cm−1) and high ( ≥ 0.1 cm −1) resolution.
TL;DR: Graner et al. as discussed by the authors improved the A0 rotational constant by using a better Fourier spectrum of ν10 and tunable diode laser spectra of the two other bands.
TL;DR: In this article, a new assignment for vibrational spectra of molecules with the normal-to-local modes transition is proposed, using information contained on the polyad phase sphere.
TL;DR: The 2ν2 level of a 1 A 1 CH2, generated by flash photolysis of ketene, has been characterized by using both stimulated emission pumping and hot-band laser-induced fluorescence as discussed by the authors.