Interaction of laser radiation with a negative ion in the presence of a strong static electric field

Abstract

Abstract. This paper provides a general theoretical description of a weakly bound atomic system (a negative ion) interacting simultaneously with two (generally strong) fields, a static electric field and a monochromatic laser field having an arbitrary elliptical polarization. The zerorange δ-potential is used to model the interaction of a bound electron in a negative ion as well as the interaction of a detached electron with the residual atom. Our treatment combines the quasistationary (complex energy) and quasienergy (Floquet) approaches. This quasistationary, quasienergy state (QQES) formalism is the most appropriate one for analysing a decaying quantum system under the influence of a periodic external perturbation. Existing QQES theory is reviewed and some new results are discussed: the Hellmann-Feynman theorem and the normalization procedure for QQES, and the definition of the dipole moment and the dynamic polarizability for a decaying atomic system (in strong static electric and/or laser fields). These results are illustrated using analytical formulae obtained from an exact solution of the QQES problem for a δ-model potential in two strong fields. Finally, from the imaginary part of the dynamic polarizability we obtain analytic results (to first order in the laser-field intensity) for the photodetachment cross section. Our results are then compared with those of previous theoretical studies.

Multiphoton detachment of a negative ion by an elliptically polarized, monochromatic laser field

“…In order to present our results in the most general form, it is convenient to use scaled units based on the single parameter κ of the model potential (8): the length unit is 1/κ; the energy and the frequency are measured in units of |E 0 | and |E 0 |/h; the field amplitude F is measured in units of the 'internal field', F 0 = 2m|E 0 | 3 /|e|h and the corresponding scaled unit of the intensity, I = cF 2 (9), which is self-consistent for the (one-parameter) δ-potential model. However, it is well known that for real negative ions more exact results may be obtained using, instead of N, a corrected normalization constant, N c , which may be obtained, e.g., by analysing the asymptotic behaviour of the wavefunction for large r (cf [29,128,140] for details). For this case, our results for the photodetachment cross sections, σ (n) , and/or probabilities should be multiplied by the renormalization factor A c = 2π N 2 c /κ.…”

Incorporating exact two-body propagators for zero-range interactions intoN-body Monte Carlo simulations

“…Nowadays, the two-body contact interaction is discussed in elementary quantum texts [2]. It has, e.g., been used to gain insights into the correlations of molecules, such as H + 2 and H 2 , and to model atom-laser interactions [3][4][5].…”

Cutoffs of high-energy plateaux for atomic processes in an intense elliptically polarized laser field

“…Our study is based on approximations to exact quantum results for the transition amplitudes within the quasienergy approach [8] for the case of a short-range potential [9,10]. Detailed analytical study of strong fi eld processes is possible only for short-range potentials U(r) (i.e.…”

“…τ 1 = 4.086): For our purposes, it is necessary to estimate the matrix element M k0 for large k: k > |z 1 | (where |z 1 | 1 for small ω and u p ω). For these parameter values, the Bessel function in (5) may be replaced by its Debye asymptotic limit [15]: (9) Since |J k ( z(τ))| has a global maximum at τ = τ 1 , the dominant contribution of J k ( z(τ)) to the integral in (5) comes from the small interval of τ centred at τ = τ 1 . Substituting in (9) x → z(τ) and expanding z(τ) up to second-order terms near the point τ = τ 1 , we obtain the following approximation for the Bessel function in (5): (10) where Using (10) to evaluate the integral in (5) for k΄ = 0, the resulting approximate value for |M k0 | is (11) where α = k -|z 1 | -ω -1 .…”