The 3←0 CH stretch overtone of benzene: An optothermal study

Abstract

The second CH stretch overtone of benzene at the rotational temperature of about 20 K has been measured in a supersonic molecular beam. Infrared absorption has been detected by means of the optothermal method. At least seven vibrational bands have been resolved in the wave numbers range from 8740 to 8870 cm−1. The main absorption peak is located around 8827 cm−1, but a significant absorption is observed also in ‘‘red’’ region of the spectrum, around 8770 cm−1. Experimental spectra have been compared with a theoretical calculation carried out following the method of Sibert et al. [J. Chem. Phys. 81, 1115 (1984)]. No free parameters have been included in the calculation in order to improve the fit with experimental data. Calculations do not provide a detailed quantitative description of experimental data. However the two spectra are qualitatively similar: (a) both are characterized by a main absorption structure located in the 8820–8840 cm−1 region and (b) calculations confirm the experimental observation that a significant part of the CH oscillator strength is borrowed by lines located on the ‘‘red’’ side of the main peak.

Vibrational overtone spectroscopy of pyridine and related compounds

“…The shift is larger in the compound with two fluorine substituents on the ring. A similar relationship between aryl CH stretching frequency and the number of fluorine substituents in benzene was described by Gough and Henry1 5 . Part of the blue shift comes from the higher fundamental frequencies in the fluorinated pyridines.…”

“…It is possible that fluorination eliminates one of the three CH local modes and splits the remaining two which were previously unresolved in the spectrum of pyridine. Gough and Henry 1 5 reported that in fluorobenzene the ortho CH stretch absorptions shifted to the blue further than the meta and para CH absorptions.…”

“…Experimental work 4 on the second overtone spectrum of jet cooled benzene indicates homogeneous linewidths as small as 4 cm-I. The absorption spectrum of jet cooled benzene displays as many as seven absorptions in the second overtone region 5 . These features are satisfactorily matched by a one dimensional vibron model calculation 6 which includes coupling of the CH stretches, the CC stretches and the in-plane CH bends.…”

High resolution rovibrational spectroscopy of pyrimidine: Analysis of the B1 modes ν10b and ν4 and B2 mode ν6b

“…In that context excited electronic states and their radiationless transitions have been discussed in detail [4][5][6][7] and also intramolecular dynamics in the electronic ground state [8][9][10][11][12][13][14][15][16][17] (for further references see [17]). …”

Quantum mechanical study of intramolecular vibrational energy redistribution in the second CH stretch overtone state in benzene

“…[2][3][4][5][6][7][8] The second overtone state CH(vϭ3) in benzene has been the object of numerous studies, both experimentally and theoretically. [9][10][11][12][13][14][15][16][17][18][19][20] From their gas phase photoacoustic spectrum of the CH(vϭ3) state, Reddy, Heller, and Berry 10 inferred a homogeneous intramolecular vibrational redistribution ͑IVR͒ bandwidth of ϳ23 cm Ϫ1 and pronounced nonstatistical ͑nonergodic͒ redistribution character. Later Page, Shen, and Lee, 12 using state selective multilevel saturation spectroscopy of rotationally jet-cooled molecules (T rot ϳ5 K) observed a central peak of 10 cm Ϫ1 width.…”