Laser photofragment spectroscopy of the NO2 dissociation at 337 nm. A nonstatistical decay process

Abstract

The dynamics of the photodissociation of the NO₂ molecule into NO(X ²Π_1/2,3/2; v, J)+O(³P_0,1,2) at the N₂ laser wavelength 337 nm (=29 965 cm⁻¹) has been investigated by laser photofragment spectroscopy at room temperature in bulk. The internal energy distribution of the NO(X ²Π) fragment has been analyzed state selectively with respect to the electronic energy (Ω=1/2, 3/2) and rotation–vibration energy (v, J) using laser induced fluorescence excitation for the NO observation by the A–X transition in the ultraviolet. The rotational and vibrational populations strongly deviate from equilibrium distribution indicating a nonstatistical decay mechanism. The partitioning of the maximum available excess energy of 4842 cm⁻¹ is about 70% into internal and 30% into recoil fragment energy. The distribution of the internal energy is about 51% into vibration and 16% into rotation of NO, with an inversion in the vibrational population of the accessible levels v=0,1,2.