Local modes of benzene and benzene dimer, studied by infrared--ultraviolet double resonance in a supersonic beam

Journal Article · Fri Apr 15 00:00:00 EDT 1988 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.453775· OSTI ID:5442357

Page, R H; Shen, Y R; Lee, Y T

We used rotational cooling of molecules to approx.5 K by supersonic expansion and state-selective, multilevel saturation spectroscopy to obtain high-resolution spectra of the fundamental and first and second overtone transitions of C--H stretching modes in ground-electronic-state benzene and its dimer. Greatly reduced linewidths (<3 cm/sup -1/ FWHM) in the rich spectra show that previously reported spectra have suffered from inhomogeneous congestion. Our observed spectral widths indicate that the vibrational lifetimes of the C--H stretches are at least a few ps, even at the energy of the second overtone (8800 cm/sup -1/). The ''local mode'' picture appears to apply when at least three quanta of C--H stretching motion are present. Spectra of the dimer are similar to those of the monomer but show a red shift of a few cm/sup -1/, the appearance of combination bands involving van der Waals vibrational modes, some intensity changes, and a broadening of spectral features that increases with the vibrational energy. The dimer's predissociation lifetime at approx.3000 cm/sup -1/ vibrational energy exceeds approx.3 ps.

• Research Organization: Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5442357
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 88:8; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
AROMATICS
BEAMS
BENZENE
COOLING
DIMERS
DOUBLE RESONANCE METHODS
FLUID FLOW
HARMONICS
HYDROCARBONS
INFRARED SPECTRA
LINE WIDTHS
MOLECULAR BEAMS
ORGANIC COMPOUNDS
OSCILLATIONS
SPECTRA
SUPERSONIC FLOW