EGAS41 - Swansea University

41 st EGAS CP 83 Gdańsk 2009
Importance of polarization potential and PCI in the (e, 2e)
processes on alkali and alkali earth targets at low energies
G. Purohit ∗ , K.K. Sud
Department of Basic Sciences, School of Engineering Sir Padampat Singhania University
Bhatewar, Udaipur-313 601, India
∗ Corresponding author: g vpurohit@yahoo.com
The study of electron impact ionization of atoms and molecules has been of interest, since
the early days of atomic and molecular physics, since the kinematics of this process are
easily controlled, and the electrons or ions resulting from the reaction can be observed with
relative ease. The electron impact ionization of atoms is a three body problem governed
by the Coulomb force acting between incident electron, target electron and residual ion.
Fundamentally an (e, 2e) process is one where an electron of well defined energy and
momentum is incident on a target, ionizes it and the outgoing electrons are detected in
coincidence with their energies and angles resolved. Ionization is a technique which is
used as a tool to probe target wave functions. Study of ionization process in different
geometrical arrangements offers a help to understand the reaction mechanism better.
Through the careful choice of geometrical arrangement and the energies of incoming and
exiting electrons one can predict the physics which will dominate the shape and magnitude
of the triple differential cross section. The calculation of triple differential cross section
opens up a whole new area of theoretical study and offers a direct insight into the subtleties
of spin-dependence and other purely relativistic effects etc. Since the first coincident
measurement of (e, 2e) process on atoms by Erhardt et al[1] and Amaldi et al. [2] extensive
theoretical and experimental investigations have been done to measure the TDCS. There
has been recent interest to study (e, 2e) processes on alkali and alkali earth atoms initiated
by measurements of Murray [3]. Recently U Hitawala et al. [4], Srivastava et al. [5] and
Bray et al. [6] have reported the results of (e, 2e) triple differential cross sections for alkali
atom Na and K. We present in this communication the results of our distorted wave Born
approximation (DWBA) calculations of TDCS for the ionization of alkali atoms Na and K
and alkali earth atoms Mg and Ca. We also include correlation-polarization potential in
DWBA formalism as a function of density function. We discuss the salient features of our
DWBA results which are different from the results of earlier workers. We will also discuss
the effects of incident electron energy, distortion, nuclear charge, correlation-polarization,
post collision interaction etc. on the trend of TDCS for alkali and alkali earth targets.
References
[1] H. Ehrhardt, M. Schulz, T. Tekaat, K. Willmann, Phys. Rev. Lett. 22, 89 (1969)
[2] U. Amaldi, A. Egidi, R. Marconnero, G. Pizzela, Rev. Sci. Instrum. 40, 1001 (1969)
[3] A.J. Murray, Phys. Rev. A 72, 062711 (2005)
[4] M.K. Srivastava, R.K. Chauhan, R. Srivastava, Phys. Rev. A 74, 064701 (2006)
[6] I. Bray, D.V. Fursa, A.T. Stelbovics, J. Phys. B 41, 215203 (2008)
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