VIBRATIONAL-RELAXATION OF ACETYLENE PRODUCED BY THE PHOTOLYSIS OF VINYL BROMIDE

Vibrational relaxation of the nu(2) and 2-nu(2) CC stretch vibrational states in the ground electronic state of acetylene has been investigated using infrared kinetic spectroscopy. Excited vibrational states of acetylene are produced by 193 nm ArF excimer laser photolysis of vinyl bromide in a room-temperature helium buffer gas. Vibrational state populations are probed by direct absorption with the continuous single-frequency output of a color center laser operating in the 3-mu-m region. The vibrational transitions observed were the nu(2) + nu(3) - nu(2) and the 2-nu(2) + nu(3) - 2-nu(2) combination bands. Rate constants for He vibrational relaxation are 1.5(3) x 10(-14) and 2.1(7) x 10(-14) cm3 molecule-1 s-1 for nu(2) and 2-nu(2), respectively.