Electron-impact rotational excitation of CH+
AJ Lim, I Rabad�n, J Tennyson�- Monthly Notices of the Royal�…, 1999 - academic.oup.com
AJ Lim, I Rabad�n, J Tennyson
Monthly Notices of the Royal Astronomical Society, 1999•academic.oup.comNew coupled-state R-matrix calculations are performed at energies up to 1 eV to give
rotational excitation and de-excitation cross-sections for electron collisions with CH+.
Rotational excitations with δ j up to 7 are considered. Transitions with δ j up to 6 are found to
have appreciable cross-sections, those with δ j= 2 being comparable to (indeed slightly
larger than) those with δ j= 1, the only ones considered previously. Rates for electron
temperatures up to 15 000 K and critical electron densities are given. A model of CH+�…
rotational excitation and de-excitation cross-sections for electron collisions with CH+.
Rotational excitations with δ j up to 7 are considered. Transitions with δ j up to 6 are found to
have appreciable cross-sections, those with δ j= 2 being comparable to (indeed slightly
larger than) those with δ j= 1, the only ones considered previously. Rates for electron
temperatures up to 15 000 K and critical electron densities are given. A model of CH+�…
Abstract
New coupled-state R-matrix calculations are performed at energies up to 1 eV to give rotational excitation and de-excitation cross-sections for electron collisions with CH+. Rotational excitations with δ j up to 7 are considered. Transitions with δ j up to 6 are found to have appreciable cross-sections, those with δ j = 2 being comparable to (indeed slightly larger than) those with δ j = 1, the only ones considered previously. Rates for electron temperatures up to 15 000 K and critical electron densities are given. A model of CH+ rotational populations shows them to be relatively insensitive to electron temperatures in the range 800–2000 K, but to depend strongly upon electron density. The models predict a significant population in rotational states with j > 1 even at low electron densities; at higher densities the possibility exists that electron collisions alone might explain the recently observed populations in the planetary nebula NGC 7027.
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