Photodetachment microscopy in time-dependent fields

Abstract

Photodetachment of negative ions in combined laser and low-frequency fields is investigated. The time-dependent Green's function method is used for calculation of electron flux at a macroscopic distance away from the photodetachment source, typical for a photodetachment microscopy experiment. In calculating the electron flux, we use the stationary phase method for the time integral, equivalent to the semiclassical approximation, to compute the time dependent wavefunction. The stationary points t (i) 1 , i = 1, ..., n correspond to time instances of launching of classical trajectories arriving at the detector at a given space-time point (r, t). The number of trajectories n contributing to the electron flux at any point in the classically allowed space-time domain can be controlled by varying the switching interval of the high frequency laser which initiates the photodetachment process. The divergences inherent in the electron flux in the semiclassical treatment are removed by using the uniform Airy approximation near the caustics.

Quantum photodetachment of hydrogen negative ion in a harmonic potential subjected to static electric field

“…As far as the impact of photon energy on cross section is concerned, it is controlled by the term (E b + E) 3 in the denominator of Eq. (19). However, the maximum value of cross section seems to originate at the particular values of the spectral parameters where their mutual harmony is optimum.…”

“…[9][10][11][12][13][14][15][16] The experimental footprints of oscillations in the photodetachment of negative ions in electric field have been observed by the photodetachment microscopy. [17][18][19][20] Photodetachment microscopy offers a wonderful practical implementation of the photodetachment process in external fields and proved to be an innovative method for the measurement of electron affinity of atoms and direct observation of the spatial structure of detached electron wave function. To further explore the efficacy of the semiclassical approach, results of COT for some physical systems have been compared with that of quantum approach.…”

Closed-orbit theory for the photodetachment rate in a static magnetic field transversely superimposed to an oscillatory electric field

“…Since the main motivation is to study the time-dependent interference induced by the external electric and magnetic fields, the laser field is used with a finite duration. The specific shape of the laser profile, in this work, is the following [8,23] where τ u and τ d account for the times when the laser field is switched on and off, respectively; whereas τ L controls the response time for the on-off process. In figure 2 we show the normalized profiles of the laser field and the external oscillatory electric field; notice that we consider the case where only one period of oscillation of E fits the envelope of the laser.…”

“…For simplicity, we assume the laser field to be turned on and off slowly enough, in this regard, the parameters of the weak laser profile (2) must satisfy [8] 2π…”

“…Photodetachment and photoionization of atoms in the presence of various configurations of external fields have been studied theoretically and experimentally in the last decades [1][2][3][4][5][6][7][8][9]. Much of the theoretical work has been done using semiclassical methods.…”