Angular momentum changing transitions in proton-Rydberg atom collisions

D. Vrinceanu (1) , R. Onofrio (2,3) and H. R. Sadeghpour (3) ((1) Texas  Southern  University,  Houston,  TX, USA; (2)Universitá di Padova, Padova, Italy; (3) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA)

Collisions between electrically charged particles and neutral atoms are central for understanding the dynamics of neutral gases and plasmas in a variety of physical situations of terrestrial and astronomical interest. Specifically, redistribution of angular momentum states within the degenerate shell of highly excited Rydberg atoms occurs efficiently in distant collisions with ions. This process is crucial in establishing the validity of the local thermal equilibrium assumption and may also play a role in determining a precise ionization fraction in primordial recombination. We provide an accurate expression for the non-perturbative rate coefficient of collisions between protons and H(n_l) ending in a final state H(n_l’), with n being the principal quantum number and l,l’ the initial and final angular momentum quantum numbers, respectively. The validity of this result is confirmed by results of classical trajectory Monte Carlo simulations. Previous results, obtained by Pengelly and Seaton only for dipole-allowed transitions, l—>l+-1, overestimate the l-changing collisional rate approximately by a factor of six, and the physical origin of this overestimation is discussed.

Complete preprint ==>

This entry was posted in Atomic data production and tagged , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s