Two-photon ionisation of ground state

and metastable helium atoms

H. Margad1, D. Khalil1, A. Makhoute1*, M. Bakkali1, M. N. Hounkonnou2

1UFR de Physique Atomique, Moléculaire et Optique Appliquée.

Faculté des Sciences. Université Moulay Ismail.

B.P. 4010, Beni M'hamed, Meknès, Morocco.

2Institut de Mathématique et Sciences Physiques,

Université Nationale du Bénin, B. P. 613, Porto-Novo, Bénin

* Corresponding author. E-mail: makhoute@netcourrier.com/ makhoute@fsmek.ac.ma

Received : 18 October 2004; revised version accepted :20 May 2005

Abstract

Non resonant multiphoton ionisation of helium from the ground state 11S, the metastable singlet state 21S and the metastable triplet state 23S are presented for linearly and circularly polarized laser field. The calculation is performed by using two different techniques, which although both relying on sturmian approach differ somewhat in the practicalities of the computation, this allows us to exactly take into account the contribution of the continuum spectrum. Our numerical results obtained are in good agreement with experimental ones.

Keywords: Laser field; Multiphoton ionisation; Resonant; Metastable; Sturmian approach; Cross section.

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