Diode Laser Study of the Rotational Redistribution in CH3OH during a Supersonic Jet Expansion

✍ Scribed by M. Hepp; I. Pak; K.M.T. Yamada; E. Herbst; G. Winnewisser

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 505 KB
• Volume: 166
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1994.1172

✦ Synopsis

After rapid cooling in a supersonic jet expansion, the populations of the lowest rotational levels of methanol have been determined from the intensities of IR absorption transitions of the (\mathrm{C}-\mathrm{O}) stretching band at (10 \mu \mathrm{m}). A newly constructed multireflection system (White type, 16 passes) has been employed for the detection of weak absorption lines. The rotational temperature of methanol has been found to be lower for the (E)-symmetry substate of the ground (\left(v_{\mathrm{r}}=0\right)) torsional state than for the (A)-symmetry substate: (T_{\text {rot }}(A-S y m)=(15.8 \pm 0.5) \mathrm{K}) and (T_{\text {ror }}(E)-Sym ()=(13.3) (\pm 0.9)) K. No torsional hot-band transitions have been observed in the jet spectrum, indicating an efficient cooling of the torsional degree of freedom. The population distribution of the probed rotational levels is strongly nonthermal, or "normal," in the sense that the (A / E) population ratio maintains its room temperature value of near unity. 1994 Academic Press, Inc.