Infrared diode laser spectroscopy of the allyl radical. The ν11 band

Abstract

Allyl radicals were generated by the photolysis of 1,5-hexadiene at 193 nm and were detected by observing the Vll, i.e., CH 2 symmetric wagging band by infrared diode laser kinetic spectroscopy. The observed spectrum showed clearly the effect of nUclear-spin statistical weights, establishing the presence of a q axis in the molecule. The spin-rotation splitting was not resolved; only some high-Ka lines were found broader than others, placing an upper limit for the Eaa constant at about 200 MHz or less. The rotational constants derived from the observed spectrum indicate that the molecule is essentially planar. The C-C bond length and the CCC bond angle were calculated from the ground-state rotational constants to be 1.3869 A and 123.96°, respectively, where structural parameters involving hydrogens were fixed to those of ab initio values.

Time-resolved photoelectron spectroscopy of the allyl radical: The lifetimes of the ultraviolet bands

“…The details of the radical source, mounted on a General Valve solenoid with a 0.8 mm nozzle, are described in the literature. 48 Number densities of more than 10 14 radicals per cm 3 can be obtained at the source exit, which yields around 10 10 radicals per cm 3 in the ionization region. The source region is pumped by a 235 ft 3 /min roots blower, while the main chamber, separated by a skimmer, is equipped with a 2400 l /s diffusion pump.…”

“…1. The ground-state geometry is known with high accuracy from IR diode laser spectroscopy, 3 while the vibrational frequencies were determined by resonance Raman spectroscopy 4 and IR spectroscopy in cryogenic matrices. 5 The location of the electronic A state was derived from an unassigned, but well resolved absorption spectrum.…”

Rotational Analysis of ν13 of Allyl Radical

“…The first rotationally resolved spectrum of allyl radical, the 11 fundamental, was reported by Hirota, Yamada, and Okunishi (1). Very recently the 1 and 13 bands have been observed in an electric discharge pulse jet apparatus (2) and by infrared kinetic spectroscopy (3).…”

“…However, the perpendicular 1 band has clearly recognizable high K a Q branches in the wings. Consequently, the initial analysis efforts for the room temperature spectrum focused on 1 . It proved possible to assign many transitions for 1 , and a complete set of ground and excited state rotational and centrifugal distortion constants were obtained for this band by combining the infrared kinetic spectroscopy data with the pulsed jet data.…”

“…Consequently, the initial analysis efforts for the room temperature spectrum focused on 1 . It proved possible to assign many transitions for 1 , and a complete set of ground and excited state rotational and centrifugal distortion constants were obtained for this band by combining the infrared kinetic spectroscopy data with the pulsed jet data. The parallel 13 band has most of its rotational structure near the highly congested double origin, and there is only one ground state combination difference check for each upper state level because the a-type Q branches pile up in a nearly unresolved origin region.…”