Photodetachment of H ⁻ near a Partially Reflecting Surface—I

Abstract

Theoretical and interpretative study on the subject of photodetachment of H − near a partial reflecting surface is presented, and the absorption effect of the surface is investigated on the total and differential cross sections using a theoretical imaging method. To understand the absorption effect, a reflection parameter K is introduced as a multiplicative factor to the outgoing detached-electron wave of H − propagating toward the wall. The reflection parameter measures, how much electron wave would reflect from the surface; K = 0 corresponds to no reflection and K = 1 corresponds to the total reflection.PACS number: 32.80.GcIt has been observed both theoretically as well as experimentally that the photodetachment cross section of H − shows a smooth behavior in the free space [1,2]; while in the presence of a reflecting surface it displays oscillations [3,4]. These oscillations are similar as if they are in the presence of a static electric field [5,6,7,8,9,10,11]. Quite recently, Afaq and Du [12] have argued that this oscillatory effect in the photodetachment cross section of H − is because of two-path interference of the detached-electron wave from the negative ion. To the observation point, one path comes directly from the source H − , while the second path appears to be coming from an image of the source behind the wall. In reference [12], the idea has been discussed without considering the absorption effect of a wall. What would happen on the photodetachment cross section of negative ion when the wall in use will be absorbing? This problem is still interesting and has to be discussed. I use a simple model for H − and provide quantitative answer to the problem.Near an absorbing wall the physical picture of the photodetachment process may be described as: When the detached-electron wave is made incident on the wall, a part of it is absorbed by the wall and the other part is reflected with low intensity. This low intensity electron wave propagates away from the system and appears to be coming from an image behind the wall, and at a very large distance it interferes with the direct outgoing detached-electron wave. Consequently, we obtain an outgoing electron flux interference pattern on the screen. The photodetachment cross section is proportional to the integrated outgoing electron flux across a large enclosure in which the source H − sits.A partial reflecting wall (0 ≤ K ≤ 1) is used for the electron scattering and it is placed from H − at a distance more than 50 Bohr radii, so that the asymptotic approximations can be valid. The assumptions about the partial reflecting wall are the same as in reference [12]. For an observer at large distance from H − , there are two components of detached-electron wave going from H − to the observer. The first component propagates directly from H − to the observer as if there is no wall; the second component first propagates toward the wall, after being partially reflected by the wall, it then propagates from the wall to the observer. In the theoretical imaging

Classification of partially reflecting surfaces using photodetached electron spectrum

“…Equation (16) provides a two term formulas, a background and an oscillatory term. The result is in agreement with the asymptotic formula derived by the author using theoretical imaging method [21]. There is a strong relationship between the reflection parameter K of the surface and the amplitude of oscillation in the absorption spectrum as is depicted in Figure 2.…”

“…One of the authors has recently introduced a theoretical imaging method for the calculation of the total photodetachment cross section from H − near an inelastic surface [21].…”

“…An (inelastic) reflecting surface is used as a detached electron scattering surface and the assumptions about the surface is the same as in Ref. [21]. Throughout the article, atomic units are used unless otherwise mentioned.…”

Detached Electron Spectra from H − near a Partially Reflecting Spherical Surface

“…( 11) recovers the results of a plane wall case reported in Ref. [17]. The value of 𝐾 depends upon the nature of the surface and varies from 0 to 1.…”

Photodetachment of hydrogen negative ion near inelastic surfaces: Arbitrary laser polarization direction

“…Now, closed orbit theory is also conveniently being used to study photodetachment of ions and molecules near surfaces. Theoretical imaging method is another useful mathematical tool to investigate problems of photodetachment process near surfaces, which is totally different approach than closed orbit theory.…”