CH[sub 3][sup 18]OH: Assignment of FIR laser lines optically pumped in the in-plane CH[sub 3]-rocking band
- Univ. of New Brunswick, Fredericton, New Brunswick (Canada). Dept. of Physics
Over 100 far-infrared (FIR) laser emission lines, with wavelengths ranging from 34 to 653 [mu]m, have been reported for the CH[sub 3] [sup 18]OH isotopomer of methanol optically pumped by CO[sub 2] lasers. Most of these FIR laser lines arise from transitions within the CO-stretching state, due to the good overlap between the CO-stretching band of CH[sub 3] [sup 18]OH and the 10.6 and 9.6-[mu]m CO[sub 2] laser bands. However, some of the FIR lines are pumped by high-lying CO[sub 2] transitions of the 9.6-[mu]m band and clearly originate from a different vibrational state. In a detailed analysis of the high-resolution fourier transform infrared spectrum of CH[sub 3] [sup 18]OH, the authors have identified the weak in-plane CH[sub 3]-rocking band lying just above the strong CO-stretching band, and have assigned 11 of the FIR laser lines to rocking-state transitions along with an additional 2 lines assigned to CO-stretching transitions. An important and unexpected finding was the existence of strong Fermi resonance between the torsionally excited n = 1 state of the rocking mode and the ground n = 0 state of the OH-bending mode, which produces significant level shifts and mixing and leads to two of the lasing transition systems. Here, the authors present the FIR laser assignments together with the spectroscopic evidence used to confirm them through combination-difference loops. The interplay between the FIR laser observations and the spectroscopic analysis has proved beneficial in supporting the assignments and in yielding information for the accurate location of levels of the elusive CH[sub 3]-rocking state.
- OSTI ID:
- 6816862
- Journal Information:
- Journal of Molecular Spectroscopy; (United States), Journal Name: Journal of Molecular Spectroscopy; (United States) Vol. 168:1; ISSN JMOSA3; ISSN 0022-2852
- Country of Publication:
- United States
- Language:
- English
Similar Records
Assignments of the high power optically pumped cw laser lines of CH/sub 3/OH
Analysis of CH/sub 3/OH far infrared laser lines optically pumped by sequence band and isotopic CO/sub 2/ lasers