Radiative lifetime and quenching cross section of the <i>B</i> 1π<i>u</i> state of K2 by time correlated single photon counting using a mode-locked He–Ne laser

Abstract

The radiative lifetime of the B 1πu state of K2* has been measured using the time correlated single photon counting technique with a mode-locked He–Ne laser excitation source. This method provides a direct means of observing the fluorescence decay while previous measurements of the K2 lifetime have involved indirect methods. The radiative lifetime and the quenching cross section for K2*–K collisions were found to be 12.2±0.2 nsec and 162±7 Å2, respectively. The photon counting technique is discussed extensively, especially in light of the use of a mode-locked laser as the excitation light source in place of the usual flashlamp. Possible quenching mechanisms for the K2 B 1πu state are also considered.