COLLISIONAL PROCESSES IN THE O2B3-SIGMA(-)(U) STATE

Collisional processes, which influence quantitative laser-induced fluo rescence (LIF) measurements involving the B (3) Sigma(u)(-) state of m olecular oxygen, were investigated. Since the B state is strongly pred issociating, these processes are thought to be important only at highe r pressures. However, we found that in LIF experiments in methane/air flames in the pressure range between atmospheric pressure and 40 bar c ollisional quenching and rotational energy transfer (RET) are importan t even at moderate pressures. Total quenching cross sections of 30(+/- 10) Angstrom(2) for v' = 2 and 100(+/- 30) Angstrom(2) for v' = 0 and total RET cross sections of 40(+/- 16) Angstrom(2) were found. An upp er limit of 0.7 Angstrom(2) for the cross section for vibrational ener gy transfer (VET) out of v' = 2 could be determined.