Multiphoton ionization of hydrogen in parallel microwave and static electric fields: Advanced simulations

Stanislav D. Tvorogov, Ljudmila I. Nesmelova

Eugene Oks, T. Uzer

The multiphoton ionization of hydrogen in strong parallel microwave and static fields is a fundamental problem of great complexity which has been the subject of recent experimental and theoretical studies. We show that the superposition of an additional field, namely a static, relatively weak magnetic field, results in rapid oscillations of the ionization survival probability. These rapid oscillations can be used as a very sensitive method for measuring weak magnetic fields.

Brian Shortt, Peter J. M. van der Burgt, F. Giammanco

We derive a set of density matrix equations describing laser photo-excitation and ionization of atomic hydrogen in the presence of an external electric field. The equations are relevant as a description of multiphoton ionization of hydrogen (or deuterium) atoms in laser-produced transient plasmas. The laser wavelength is 243 nm, so that the photoionization is resonant with the 2 s 1/2 level. The electric field causes Stark mixing of the 2 s 1/2 level with the 2 p 1/2 and 2 p 3/2 levels. Because the electric field is taken in the same direction as the linear polarization of the laser, only states with equal m j are coupled, and the atom can be described with a four-level density matrix. The laser bandwidth is taken into account by using the stochastic model of a chaotic laser field introduced by Zoller [1]. We present a few calculations of the probabilities for ionization and excitation of a single hydrogen atom as a function of laser intensity and wavelength.

D. E. Kelleher, M. Ligare, L. Brewer

Jianguo Rao, Baiwen Li, K T Taylor

We refine an earlier method for calculating the spectra of atoms and molecules in a strong microwave or laser field plus a static electric field. Results are reported for microwave resonance transition spectra of potassium for transitions from the 19s state at five choices of fixed microwave field strength (38, 68, 120, 152 and 193 V cm(-1)) as the static field strength is varied from 200 to 550 V cm(-1). More resonances have been found in the higher microwave field-strength theoretical spectra than previously found experimentally. An understanding of butterfly like structures in the plot of quasi-energy against static electric field strength has allowed an improved understanding of these novel features.

Erna Karule