Atomic and Molecular Physics
External Funding

Atomic and Molecular Physics

Atomic and molecular states in weak and strong external static and ac electromagnetic fields

When the interaction of strong fields with atomic and molecular states can be cycle-averaged, which includes the case of static fields, it is possible to tackle theoretically and computationally related physical problems in terms of a complex eigenvalue, many-electron many-photon theory, in which the full Hamiltonian is diagonalized by a properly optimized, state-specific complex wavefunction consisting of real and of complex basis functions and having the form, e.g., [1,2],

where is a complex coordinate.
The solutions provide quantitative answers for properties and phenomena such as multiphoton single and multiple ionization in polychromatic fields, above threshold ionization, high order harmonic generation, dynamic polarizabilities and hyperpolarizabilities etc.. For example, the figure below shows He multiphoton ionization rates ( in a.u.) in the laser frequency ( in a.u.) region where at least 3 photons are necessary for ionization. The intensity varies from 3.5x1012 W/cm2 up to 1.7x1014 W/cm2. The peaks correspond to (2+1) resonant enhanced multiphoton ionization with the 1sns 1S, 1snd 1D (n=...,6) states.

In the case of polychromatic fields, the structure of the theory is such that it allows the quantitative study of control of the multiphoton ionization processes as a function of the phases of the fields, e.g. [3].

[1] 'Atoms in Strong Fields' , eds. C. A. Nicolaides, C. W. Clark and M. H. Nayfeh, Plenum Press, New York, (1990)
[2] Th. Mercouris and C. A. Nicolaides, 'Solution of the many-electron, many-photon problem for strong fields: Application to in one-and two-color laser' Phys. Rev. A 67, 063403 ((2003).
[3] Th. Mercouris,C. Haritos and C. A. Nicolaides, 'Interference generalized cross-setion for the multiphoton detachment of in dichromatic fields', J. Phys. B 38 , 399 (2005)

TPCI Staff
Researchers: Y.Komninos, T. Mercouris
Collaborating Faculty Member: C. A. Nicolaides

T. Mercouris and C. A. Nicolaides
Theoretical and Physical Chemistry Institute,
National Hellenic Research Foundation,
48 Vassileos Constantinou Ave.,
Athens 11635, Greece

Tel.: +30 210 7273804, 7273809
FAX: +30 210 7273794
Email: thmerc, caan







National Hellenic Research Foundation (NHRF), 48 Vassileos Constantinou Ave., 11635 Athens, Greece, Tel. +302107273700, Fax. +302107246618