Field-assisted photodetachment process to observe the ponderomotive shift

Abstract

Two-color photodetachment of a negative ion in the presence of a constant magnetic field is proposed as a process in which to observe the ponderomotive shift. Appropriate calculations are reported of the process under consideration based on a simple one-electron model and with the basic physical parameters well within the experimental state of the art.PACS number(s): 32.80.Rm

A comment on the validity of an approximation method for two-colour photodetachment

“…It is the aim of this comment to show that when the approximate expression of the S-matrix element quoted by Bivona et al (1994) is correctly treated, cross sections are obtained that are in agreement with the Wigner law, contrary to the affirmation of Robinson. Moreover, it will be shown that the corrections to the wavefunction of the bound state suggested by this last author do not significantly affect the values of the photodetachment cross sections calculated by using the procedure proposed by Bivona et al (1994).…”

“…It is the aim of this comment to show that when the approximate expression of the S-matrix element quoted by Bivona et al (1994) is correctly treated, cross sections are obtained that are in agreement with the Wigner law, contrary to the affirmation of Robinson. Moreover, it will be shown that the corrections to the wavefunction of the bound state suggested by this last author do not significantly affect the values of the photodetachment cross sections calculated by using the procedure proposed by Bivona et al (1994). In the E-gauge the exact expression of the S-matrix that describes the photodetachment event is given by where i is the wavefunction of the electron interacting with both the static potential V (r) and the radiation field, which tends to the bound bare state i (r, t) when the radiation field is turned off, and f is the wavefunction describing the free electron driven by the electromagnetic field.…”

“…In order to simplify his analysis, he chose to investigate the validity of the approximation for B = 0, thus reducing to the case in which the photodetachment occurs in the presence of the sole LF field. We remark that this problem along with the two-colour atom ionization has recently been treated by several authors (see, for instance, Mittleman 1989, Abranys and Mittleman 1990, Becker et al 1989, 1990a, Gao 1990, Bivona et al 1992.…”

“…Recently, Robinson (1995) investigated the validity of an approximation method used by Bivona et al (1994) for two-colour photodetachment in the presence of a static magnetic field B, raising serious doubts on the reliability of the cross section obtained by its application. The starting point of the criticism of Robinson is the approximate form of the S-matrix element connecting the initial (bound) state of a negative ion to a final (free) state dressed by a low-frequency (LF) electromagnetic field.…”

“…The conclusion of Robinson is that the treatment used by Bivona et al (1994), while possibly valid for some S-matrix element, may lead to results which are affected by order of magnitude errors.…”