Beam study of the luminescent E-E energy transfer reaction Kr(3P2)+N2→Kr+N2(B 3Πg) at high resolution and variable collision energy

Colliding a beam of metastable Kr atoms with an N-2 gas target, the resulting N-2(B (3)Pi(g) --> A (3)Sigma(u)(+)) emission was observed with a spectral resolution of up to 0.15 nm fwhm. Optical multichannel detection was employed, using a cooled diode array detector. This allowed the first rotationally well-resolved product emission spectra from the Kr* + N-2 reaction to be obtained. Also, the beam energy was varied between 69 and 191 meV(CM) by seeding with H-2. The rovibrational product distributions were derived from spectral simulations. In agreement with the literature, nonresonant (exothermic) E-E transfer was observed, populating the vibrational levels N-2(B,nu'=4-12). This broad distribution was found to be essentially independent of the collision energy. The product rotation could be well described by Boltzmann distributions with T-rot = 1300-1050 K for nu' = 5-12 at low and 1750-1400 K at high collision energy. A discussion of the reaction mechanism is given in terms of two alternative models, involving either an intermediate ion pair formation or a direct covalent curve crossing. Comparisons are made with the related reactions of Ar and Xe metastables.