Trace detection of benzene vapour in a simple ion chamber employing laser-induced resonance-enhanced multiphoton ionization in the 246–264 nm wavelength region

Abstract

A tunable, pulsed laser source has been used to ionize trace amounts of benzene vapour in a simple ionization chamber. By scanning the laser wavelength over the ¹B_2u–¹A_1g transition of the benzene molecule, it is possible to differentiate the contribution to the total ionization yield due to the resonance-enhanced multiphoton ionization (REMPI) of the benzene sample from that due to background ionization from other unidentified molecular species. The wavelength-dependent ionization fingerprint of benzene is verified by comparison with that of benzene vapour recorded in a laser TOF mass spectrometer.