Knowledge Bank

Our study of vibrational and rotational relaxation of gas phase diatomic sulfur, selectively excited to the $B3\Sigma u-$ state by atomic line emission, has recently been extended to include the effects of collisions on zero-field level crossings. From the broadening of the level crossing (Hanle effect) signal with increasing pressure of rare gas collision partners, together with direct level crossing measurements on fluorescence from rotationally transferred $S2$ molecules, we can estimate the amount of coherence retained throughout a rotational transfer collision. The degree of retention is quite high -- of the order of 80% in the case of collisions with helium.