Hot Bands in Overtone Absorption Transitions: High Temperature Spectra
Abstract
The laser photoacoustic spectra of the 4v sub N-H and 4v sub C-H overtones of pyrrole, the 5v sub c-H of methyl isocyanide and acetonitrile, the 5v sub c-H and 6v sub C-H of isobutane, and the 6v sub c-H of cyclohexane were measured at temperatures up to 140 C (T sub 140) and compared to the room temperature (T sub rt) spectra. Hot bands were identified by their temperature dependence in pyrrole, methyl isocyanide and isobutane. From the change in the relative intensities of the hot band to the main band going from T sub rt to T sub 140, the wavenumbers of the thermally populated states were 405+/-80, 410+/- 80 and 208+/-40 /cm for pyrrole, isobutane and methyl isocyanide, respectively. These values compare well to the bending motion frequencies in these molecules. Large red shifts of the hot bands from the main peak were observed, as expected for high overtone transitions due to large anharmonicities. The anharmonic constants determined from these shifts are -25 /cm for the N-H in pyrrole and - 20 /cm for the C-H in methyl isocyanide and isobutane. In the case of the N-H absorption the hot band was completely separated from the transition. In the C-H overtone spectra these hot band absorptions were not separated and result in an apparent increased width of the overtone transition.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 17, 1993
- Accession Number
- ADA262213
Entities
People
- Deanne Snavely
- Salah Hassoon
Organizations
- Bowling Green State University