Beam Study of the Luminescent E-E Energy Transfer Reaction Kr(~3P_2) + N_2 → Kr + N_2(B ~3Π_g) at High Resolution and Variable Collision Energy

摘要

Colliding a beam of metastable Kr atoms with an N_2 gas target, the resulting N_2(B ~3Π_g→A ~3Σ_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,v'=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 v' = 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.