PNNL

Abstract

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The infrared (IR) spectrum of propyne in the region of 2934–2952 cm-1 has been recorded by the IR–vacuum ultraviolet (VUV)–photoion method. The spectrum is shown to consist of two near-resonant, but noncoupled vibrational bands: the ?2 symmetric methyl C–H stretching vibrational band and a combination vibrational band ?cs. The previously unobserved Q line of the ?cs band is observed. The rotational transition lines of the ?2=1 band produces IR-VUV–pulsed field ionization–photoelectron (IR-VUV-PFI-PE) signal at the C3H4 + (?2?=1) photoionization threshold. The rotational transition lines associated with the ?cs band do not produce IR-VUV-PFI-PE signal. Rotational transition lines of both vibrational bands are assigned and simulated; and ab initio calculations further confirm the assignment.