Dissociative recombination studies of Ar+2 by time-of-flight spectroscopy
Abstract
From time-of-flight spectra of metastable Ar* atoms emerging from sustained discharges in Ar, we observe discrete nonthermal peaks due to excited products of dissociative recombination (DR) of Ar+2 formed by reactions in the discharge. These peaks are in addition to the expected Boltzmann distributions of metastable atoms from direct excitation by fast primary electrons. From the peak velocities, and thus the kinetic energies released in the dissociation, the DR product states are uniquely determined, regardless of subsequent radiation. As we have previously found from Kr+2 [A. Barrios et al., Phys. Rev. Lett. 69, 1348 (1992)], most of the excited DR products are (n+1)s states, but Ar+2 also yields smaller amounts of 4p and 3d states. We have also recently shown [G. B. Ramos et al., Phys. Rev. A 51, 2945 (1995)] that, surprisingly, in studies of Ne+2 and Ar+2 DR, a substantial but undetermined fraction of reactions go to a purely ground-state channel. In addition, we have found that under certain conditions in Ar discharges, the relative amount of the higher excited-state products, including 4p, 3d, 5s, and 5p can be dramatically influenced. The velocity peaks also become narrower than expected from the thermal distribution of the parent Ar+2 as the energy level in the product atom increases. These studies in argon discharges have included variations in source pressure, discharge voltage, and strength of the axial magnetic field.
- Publication:
-
Physical Review A
- Pub Date:
- December 1995
- DOI:
- 10.1103/PhysRevA.52.4556
- Bibcode:
- 1995PhRvA..52.4556R
- Keywords:
-
- 34.50.Lf;
- Chemical reactions energy disposal and angular distribution as studied by atomic and molecular beams