The influence of the ultra-short pulse wavelength on the populations in the three electronic states of CsI molecule is investigated using the time-dependent wave packet method. The calculated results show that the populations in the two excited states approach to the maxima at the wavelengths of 369 nm and 297 nm, respectively. The photodissociation reaction channels of the CsI molecule can be chosen by controlling the pump pulse wavelength.
Based on closed-orbit theory,the influence of an interface modifier on the photodetachment of H- in an electric field near a metal surface is studied.It is demonstrated that the interface strengthens the oscillations in the photodetachment cross section.However,when the electric field environments are different,the strengthening oscillations are caused by different sources.When the electric field direction is upward,the interface enhances the oscillations by shortening the period and the action of the closed orbit.When the electric field direction is downward,the interface strengthens the oscillations either by extending the coherent energy range or by increasing the total number of the closed orbits.We hope that our results will be conducive to the understanding of the photodetachment process of negative ions near interfaces,cavities and ion traps.
According to the semi-classical theory, we study the photodetachment microscopy of H- in the electric field near a metal surface. During the photodetachment, the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector. The electron flux distribution is measured as a function of position. Two classical paths lead the ion to any point in the classically allowed region on the detector, and waves traveling along these paths produce an interference pattern. If the metal surface perpendicular to the electric field is added, we find that the interference pattern is related not only to the electron energy and the electric-field strength, but also to the ion-surface distance. In addition, the laser polarization also has a great influence on the electron flux distribution. We present calculations predicting the interference pattern that may be seen in experiment. We hope that our study can provide a new understanding of the electron flux distribution of negative ions in an external field and surface, and can guide future experimental research on negative ion photo-detachment microscopy.
The influence of electric field on the photodetachment of H-near a metal surface is investigated based on the closed-orbit theory.It is found that the photodetachment of H-near a metal surface is not only related to the electric field strength but also to the electric field direction.If the electric field is along the +z axis,it can strengthen the oscillation in the photodetachment cross section.However,if the electric field is along the -z axis,since the direction of electric field force is opposite to that of static-image force caused by the metal surface,the situation becomes much more complicated.When the electric field is very weak,its influence can be neglected.The photodetachment cross section is nearly the same as that when a single metal surface exists.When the electric field strength is strong enough,the electric field force is able to counteract the metallic attraction,therefore no closed orbit is formed.If the electric field continues to increase until its influence becomes dominant,the photodetachment cross section approaches the case of the photodetachment of H- in an electric field.Our results may be useful for guiding future experimental studies on the photodetachment of negative ions near surfaces.
By using the closed orbit theory,the photodetachment cross section of H-near a metal surface is derived and calculated.The results show that the metal surface has great influence on the photodetachment process.As the ion-surface distance is very large,the influence of the electrostatic image potential caused by the metal surface becomes small and can be neglected.The period,action,and length of the detached electron's closed orbit are nearly the same as the case of the photodetachment of H-near an elastic interface.However,with the decrease of the ion-surface distance,the influence of the metal surface becomes significant.The amplitude of the oscillation in the photodetachment cross section becomes complicated.Each resonance peak in the Fourier transformed cross section is associated with one electron's closed orbit.Unlike the case of the photodetachment of H-near an elastic interface,the length of the closed orbit does not equal the twice distance between the ion and the surface.But with the increase of the ion-surface distance,the length of the closed orbit approaches the case of the closed orbit near an elastic interface,which suggests the correctness of our method.This study provides a new understanding on the photodetachment process of H-in the presence of a metal surface.
