Abstract
Molecular bands associated with the ND(A-X), ND(c-a), ND+(B-X), and ND+(C-X) transitions, as well as atomic lines of Balmer series and several He and He+ lines, were observed in the collisions of He+ with ND3 gas target at energies between 17 eV and 833 eV in the center-of-mass frame. Absolute luminescence cross sections, excitation functions, and the ND(c-a)/ND(A-X) branching ratios (BR) were determined. The sum of all luminescence cross sections in the 200–600 nm spectral window is below 1 × 10-20 m2 at 833 eV. The ND(c-a)/ND(A-X) luminescence BR increases with collision energy from BR = 0.20 at 20 eV to BR = 0.30 at 150 eV and up to 833 eV. Computer simulations of the spectra were used to estimate rotational and vibrational temperatures of the products. The population distributions of rotational and vibrational states of ND∗(A, c) do not vary appreciably with collision energy.Graphical abstract
Highlights
The early studies of collision induced dissociation of ammonia used ionic atomic and molecular projectiles and involved mostly mass spectroscopic detection of the products [9,10,11,12,13]
The goal of the present study is to investigate the optical emission in the 200–600 nm spectral range for the He+ ions colliding with ammonia at ECM from 17 eV to 833 eV and in this way to extend the studies of reference [4] to the lightest rare gas ion
The recorded spectra enable measurements of luminescence cross sections and the determination of population distributions of the product states described by vibrational (Tvib) and rotational (Trot) temperature parameters
Summary
The early studies of collision induced dissociation of ammonia used ionic atomic and molecular projectiles and involved mostly mass spectroscopic detection of the products [9,10,11,12,13]. The spectra of NH∗ were observed when NH3 was bombarded with carbon C+ ions or with hot neutral carbon atoms [25], for these systems the electronically excited imidogen was formed by collision-induced dissociation and as a result of chemical reactions involving atom transfer. The recorded spectra enable measurements of luminescence cross sections and the determination of population distributions of the product states described by vibrational (Tvib) and rotational (Trot) temperature parameters. The latter results are achieved by comparing the experimental spectra with the contours obtained by computer simulations. The isotopic effect on vibrational and rotational energy levels causes the ND(AX, c-a) spectra of the products to contain more lines, as more rovibronic levels lie below the value of internal energy at which predissociation of the ND(A 3Π) and ND(c 1Π) states begins depletion of emitters
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