High resolution FTIR spectroscopic study of the ν4 band of CH3CHF2 enclosed in a flow of cold N2 gas

✍ Scribed by Dominique R.T. Appadoo; Evan G. Robertson; Don McNaughton

• Book ID: 104151705
• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 376 KB
• Volume: 217
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1016/s0022-2852(02)00030-9

✦ Synopsis

An enclosive flow cooling (EFC) cell has been constructed, and coupled to a Br€ u uker IFS 120HR high resolution Fourier transform spectrometer to record rotationally cold absorption spectra of gases of atmospheric interest at high spectral resolution. The new system has been characterized using N 2 O, revealing that rotational temperatures as cold as 110 K are readily attainable using liquid nitrogen as a cryogen. Infrared spectra of the m 4 band of 1,1-difluoroethane (R152a), CH 3 CHF 2 , cooled in the EFC cell have been measured at a resolution of 0.0019 cm À1 . Eight hundred and twenty rovibrational transitions of the weak m 4 band with 2 6 J 0 6 46 and K 0 c 6 16 were assigned and fitted to WatsonÕs A-reduced Hamiltonian. The m 4 CH 3 symmetric deformation (a/c-type) was found to be coupled to the m 13 asymmetric deformation (b-type) via an a-axis Coriolis interaction. In the ensuing analysis, values of spectroscopic constants were obtained for both the m 4 and dark m 13 states. Supporting ab initio calculations up to the MP2/ TZV+(3df,3p) level are presented.