THE COLLISIONAL QUENCHING OF I(52P1/2) BY THE MOLECULES H2O, CH3OH, C2H5OH, HCOOH AND CH3COOH BY TIME-RESOLVED EMISSION (I(52P1/2)-]I(52P3/2)+HV,LAMBDA=1.315-MU-M) FOLLOWING PULSED-LASER PHOTOLYSIS

The collisional quenching of electronically excited iodine atoms, I(5p5(2P1/2)), by the molecules H2O, CH3OH, C2H5OH, HCOOH and CH3COOH was investigated directly in the time domain. I(2P1/2) was generated by the pulsed excimer laser photolysis of C3F7I at lambda = 248 nm and monitored by time-resolved emission at lambda = 1.315-mu-m (I(2P1/2 --> I(2P3/2) + h-nu). Absolute second-order quenching rate constants (k(Q)), including those for the collisional removal of the excited atom by the dimers (HCOOH)2 and (CH3COOH)2, were obtained for room temperature. The following results were obtained: [GRAPHICS] These results indicate that the main route for removal is the electronic energy transfer in the iodine atom to the second vibrational level in the O-H stretching mode in each case, via long-range attractive forces, probably involving dipole-quadrupole interaction on collision.