QUENCHING OF SINGLE ROVIBRONIC STATES OF METHYLENE 1B1

The quenching rate constants by noble gases of selected rotational lev els in the B-1(1) (0, 13, 0), (0, 14, 0), (0, 15, 0) and (0, 16, 0) be nding overtones have been measured. The initially populated levels are affected by various types and degree of perturbations; B-1(1) rovibro nic levels with K(a) not-equal 0 are perturbed by 1A1 and B-3(1) state s via Renner-Teller effect and spin-orbit interaction respectively, th ose with K(a)=0 are not affected by perturbations by other electronic states. A certain degree of correlation between the measured quenching rate constants and the perturbations affecting each selected rovibron ic state has been observed. Rates of quenching of K(a)=0 levels in (0, 14, 0) and (0, 16, 0) overtones increase with rotational excitation e xcept for the heavier noble gases krypton and xenon. Levels with K(a) not-equal 0 in (0, 13, 0) and (0, 15, 0) overtones do not manifest a r otational dependence in their quenching rate constants, which are fast er, at least by a factor of two, than those corresponding to K(a)=0 le vels. Among the studied K(a) not-equal 0 levels, those which are Zeema n active and therefore have a certain degree of triplet character tend to quench more efficiently. These results are discussed in the light of collision-induced inter-electronic energy transfer theories develop ed by Freed et al. The role of rotational relaxation and of the pertur bed gateway states is included in the discussion of the experimental r esults.