摘要:

The mechanism by which two electrons are ejected by a helium atom subjected to an intense laser field has been the subject of debate during the past decade. The consensus today in the community is that the second electron is ejected after the first one returns to the ionic core and rescatters. However, the specific details as to how this second electron is ejected remain uncertain. In this paper, we consider this process from two both quantal and semiclassical viewpoints, and propose a qualitative way of understanding how the second electron is ejected from a helium atom. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449306

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

We discuss theoretical insights gained recently in understanding the experimental results of the observed momentum distributions of doubly charged recoil ions produced by femtosecond laser pulses in terms of a non-sequential ionization mechanism. The prominent characteristics are explained based on a combined influence of Coulomb correlation between the two electrons in the intermediate state and the field dressing in the final state. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449307

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

A formalism is presented to experimentally determine the shapes, magnitudes, and relative complex phase of the correlation functionsfgandfuwhich govern the photo-double ionization process in helium. The formalism is applied to a data set from a COLTRIMS measurement of helium double ionization at 99 eV photon energy. With the results of this procedure it is possible to predict all observables of helium photo-double ionization at this energy, with the exception of the direction of the circular dichroism and of the spins. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449308

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

Recent measurements are presented of the triple differential cross section for electron impact ionization of the inner valence shells of argon and krypton at low to intermediate energies, and both coplanar symmetric and asymmetric geometries. Comparison is made with some of the latest available theoretical calculations performed in the distorted wave Born approximation formalism. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449309

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The e,2e reaction of atomic and diatomic lithium is studied. In the atomic case, the problem is treated as a four electron system for which the conservation of the total spin produces a variety of exchange terms whose importance in the determination of the transition matrix element of the ionization process is studied systematically in a very large domain of incidence energy (50 eV to 5 keV) by applying in the small and intermediate energy domain an asymptotically exact distorted wave procedure. In the diatomic case, a model potential is employed for the K shell electrons and the problem is treated as a vertical transition from the lowest vibrational and rotational level of the fundamental electronic state1&Sgr;gofLi2to the fundamental2&Sgr;gstate ofLi2+.The comparison with experimental and recent theoretical results shows that the use of an all electron procedure improves the agreement with the experimental results. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449310

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

An experiment has been performed in which a polarized electron beam ionizes an orbitally oriented and/or spin polarized valence electron of sodium. The cross section for this reaction is measured for well-resolved vector momenta of the two electrons in the final channel. A tensorial re-coupling scheme has been developed in which the measured quantities are expressed in terms of independent, irreducible spherical tensor components. For a comparison with experiment we performed numerical ionization-cross section calculations within the Distorted Wave Born Approximation (DWBA) and the Dynamically Screened Three Coulomb Waves (DS3C) theory. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449311

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

Binary (e,2e) spectroscopy (also known as EMS) is applied to problems of chemical interest including imaging of orbital electron densities, electron transfer processes, investigation of different orbital models, the evaluation of wavefunctions and computational methods for larger molecules, frontier orbital electron densities in pharmaceuticals, and distorted wave effects at low momenta for&pgr;*type MOs. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449312

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

The(VA+,Ve,P)vector correlation method for the study of dissociative photoionization (DPI) of a diatomic molecule AB, induced by linearly polarized synchrotron radiation (P), is presented. On the experimental side, imaging and time resolved coincidence techniques are combined to measure theVA+andVevelocity vectors for each DPI event. The information derived from the ion-electron kinetic energy correlation, and from the spatial analysis of the vector correlation, is illustrated on specific examples of dissociative photoionization of NO andO2following excitation of inner-valence electrons in the 20–25 eV photon energy range. Based on the general form of the molecular frame photoelectron angular distributions (MFPAD) reported here for linear molecules excited by linearly polarized light, we discuss in particular the new information gained from the azimuthal dependence of theI(&thgr;,&fgr;)distribution, for each orientation of the molecular axis with respect to the polarization. The measured MFPADs are compared with recent calculations using the multichannel Schwinger configuration interaction method. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449313

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

In atoms and molecules alike, electron-electron coincidence spectroscopies (e-e) have been extensively applied to study single particle as well as correlated properties of the target. Recent years have witnessed the first successful (e-e) on solids and surfaces. The experimental effort undertaken in order to apply (e-e) to solids is twofold. On one hand the realization of photon induced resonant double photoionization, i.e. core ionization followed by autionization (Auger) process in which Auger and photoelectron are detected in coincidence (APECS). On the other hand the realization of direct single electron ionization of valence states where both final electrons are detected in coincidence and discriminated in energy and momentum. In the first case, value and limitations of the so called two step mechanism for core ionization/relaxation processes is under scrutiny. In the second case, the possibility of direct measurement of binding energy and momentum distribution is under test. Although many aspects of these experiments are common to gas phase and condensed matter, some noticeable differences do exist; most of them amounting to final state interaction with the periodic potential that sustains the electronic states of the solid target. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449314

出版商:AIP    

年代:1902

数据来源: AIP

摘要:

In this work we discuss the influence of electronic correlation in finite and extended systems. In particular we stress the fact that the electronic correlation renormalizes the particle-particle interaction in a characteristic way and interpolate these ideas, well-known for extended systems, to small systems. We also sketch briefly how the thermodynamics and critical phenomena in finite systems may be treated. ©2002 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1449315

出版商:AIP    

年代:1902

数据来源: AIP