Resonance enhanced two-photon ionization studies in a supersonic molecular beam: Bromobenzene and iodobenzene

The 1B2(ππ*)←1A1 absorptions of two monosubstituted halobenzenes have been investigated using resonance enhanced two-photon ionization in a pulsed supersonic molecular beam. Detection of the photoions was accomplished by means of a time-of-flight mass spectrometer. The 1B2←1A1 system of bromobenzene has been observed with good sensitivity using this technique, even though the total decay rate of the 1B2 state is greater than 1×1011 sec−1. No ion signal was observed when the same transition was probed in iodobenzene, allowing us to place a lower limit on its decay rate of 4×1013 sec−1.