S-T conversion induced by external magnetic field in gaseous oxalylfluoride excited to the 7(1)5(1)-level of the (A)over-tilde(1)A(u) state

Fluorescence decay of gaseous oxalylfluoride (COF)(2) excited to the (A) ov er tilde (1)A(u)(7(1)5(1)) level was measured as a function of gas pressure in absence and in presence of magnetic field, B=0.3 T. On excitation to th is level, the dynamics in both zero and nonzero fields may be described in the intermediate-molecule limit, with the fluorescence exhibiting biexponen tial and triexponential decay, respectively. The fast component decay rate constant k(f)=(5.31 +/- 0.22). 10(7) s(-1) is independent on the (COF)(2) g as pressure or magnetic field strength, while that of the first slow compon ent depends on both. The second slow component lifetime is independent of t he field strength, while dependent on the gas pressure. The Stern-Volmer de pendence, measured with a field in the 0.3-12 mTorr pressure range, is nonl inear. The results obtained were explained by the indirect (electronic- and nuclear-spin-decoupling) mechanism, proposed earlier. (C) 2000 American In stitute of Physics. [S0021-9606(00)01925-5].