High Resolution Fourier Transform Emission Spectroscopy of Transient Molecules Using a Corona Excited Supersonic Expansion Source

Abstract

A corona excited supersonic expansion (CESE) source (1) has properties that are well suited to the study of transient molecular species with a high resolution Fourier transform spectrometer. This source is run with a continuous dc discharge and a high speed Roots pumping system. The source of transient molecules is relatively confined and quite intense when compared to flowing afterglow or hollow cathode sources. The discharge serves not only to produce the transient molecules, but also to excite the desired molecules into high electronic states, which can be observed by emission in the ultraviolet and visible spectral regions. The supersonic expansion of the source rotationally cools the transients, thereby reducing spectral congestion from overlapping bands and reducing the Doppler line width of the rotational transitions.