INFRARED, RESONANCE ENHANCED MULTIPHOTON IONIZATION DOUBLE-RESONANCE DETECTION OF ENERGY-TRANSFER IN NH3

2+1 resonance enhanced multiphoton ionization (REMPI) spectroscopy has been utilized to probe the temporal evolution of the rovibrational distribution of vibrationally excited NH3 following infrared excitation. High resolution, 2+1 REMPI spectra of the origin of the C̃′←X̃ transition of NH3 are presented and the rotational assignments are discussed. In addition, high resolution spectra of the hot band origin are obtained for the first time and rotational assignments are made. The time evolution of some specific JK states of the X̃(2, + ) and X̃(2 1- ) levels are reported, and collisional energy transfer between them is discussed. The rate constant, k1-1+, for the energy transfer process: X̃(21 +)→X̃(21-) is determined to be 0.21 μs-1 Torr-1: 50 times slower than the hard-sphere, single-collision rate and about 100 times slower than in the ground vibrational state. © 1990 American Institute of Physics.