Vibrational predissociation of benzene dimers and trimer by the crossed laser-molecular beam technique

Journal Article · Thu Oct 29 00:00:00 EST 1981 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j150622a024· OSTI ID:6071361

Vernon, M F; Lisy, J M; Kwok, H S; Krajnovich, D J; Tramer, A; Shen, Y R; Lee, Y T

A molecular beam composed predominantly of benzene monomer, dimer, and trimer is excited with tunable, pulsed, infrared radiation in the C-H stretch frequency range (3000 to 3100 cm/sup -1/). Two types of experiments are performed for the observation of the vibrational predissociation of the excited cluster, measuring directly the wavelength dependence of the predissociation yield and the translational energy distribution of the predissociation products. The wavelength dependence of the vibrational predissociation is found to be similar to the infrared spectra of room-temperature liquid benzene. The translational energy distributions of the predissociation products are used to deduce dynamical properties for the following predissociation mechanism: (C/sub 6/H/sub 6/)/sub n/ + hv ..-->.. (C/sub 6/H/sub 6/)/sub n-1/ + C/sub 6/H/sub 6/** (tau), where ** indicates vibrational excitation. The lifetime, tau, of the vibrationally excited clusters is determined to be in the range of 10/sup -12/ < tau < 10/sup -6/ s. The most probable predissociation is characterized by all of the excess energy appearing in the rotational and vibrational motions of the products. The two product molecules do not seem to share this excess energy equally, the monomer product retaining in excess of 2/3 of the available energy. These observations are qualitatively consistent with current theories of vibrational predissociation of weekly bound molecular clusters.

• Research Organization: Lawrence Berkeley Lab., CA
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6071361
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 85:22; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
AROMATICS
BEAMS
BENZENE
CHEMICAL REACTIONS
DECOMPOSITION
DIMERS
ELECTROMAGNETIC RADIATION
HYDROCARBONS
INFRARED RADIATION
IRRADIATION
LASERS
MOLECULAR BEAMS
MONOMERS
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PRESSURE DEPENDENCE
PULSED IRRADIATION
RADIATIONS