Lorentz ionization of atoms in a strong magnetic field

Lorentz ionization emerges due to the motion of atoms or ions in a strong magnetic field. We use the semiclassical approximation to calculate the probability w _L of Lorentz ionization. We also find the stabilization factor S, which takes into account the reduction by the magnetic field of the probability of ionization decay of the bound s state. We estimate the probabilities w _L in magnetic-cumulation experiments and in astrophysics. We also qualitatively examine the dynamics of the magnetic cumulation process with allowance for the conductivity of the shell. Finally, we discuss a paradox related to the use of the quasistationary solution at the shell expansion stage. Zh. éksp. Teor. Fiz. 115, 1642–1663 (May 1999)     

Effect of a magnetic field on transit time of excited atoms in a dc arc plasma

Transit times of excited atoms in a dc arc plasma exposed to an inhomogeneous magnetic field are investigated at different values of the magnetic induction. At the optimal value, the transit time, electron pressure and spectral line intensities are maxima. The large increase of spectral line intensity is not proportional to the slight increase of transit time. The transit times of different atoms at the same value of the magnetic induction are approximately equal, whereas the spectral line intensities are different. The maximum transit time corresponds to minimum electron mobility. The arc-plasma temperature is directly proportional to the magnetic induction.     

Controlled suppression of ionization of Rydberg atoms in a microwave field

A computational procedure for controlling the stochastic ionization of one-dimensional single electron Rydberg atoms in the correspondence principle regime is developed. Using our procedure it is possible to suppress excitation and ionization of the one-dimensional Rydberg atom even in strong microwave fields for which ionization would otherwise be instantaneous.     

Tunneling and above-barrier ionization of atoms in a laser radiation field

Calculations are made of the energy and angular distributions of photoelectrons during tunneling ionization of an atom or an ion under the action of high-power laser radiation (for all values of the Keldysh parameter γ). Cases of linear, circular, and elliptic polarizations of the electromagnetic wave are considered. The probability of above-barrier ionization of hydrogen atoms in a low-frequency laser field is calculated. Formulas are given for the momentum spectrum of the electrons when an atomic level is ionized by a general type of alternating electric field (for the case of linear polarization). An analysis is made of tunneling interference in the energy spectrum of the photoelectrons. Analytic approximations are discussed for the asymptotic coefficient C _κ of the atomic wave function at infinity (for s-wave electrons).     

Effect of a magnetic field on thermally activated tunneling ionization of impurity centers in semiconductors

An expression for the probability of thermally activated tunneling ionization in an electric field in the presence of a magnetic field is obtained. It is shown that the logarithm of the ionization probability is proportional to the squared electric field, and the coefficient of proportionality decreases with increasing magnetic field. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 763–767 (25 November 1998)     

Zeeman slowing atoms using the magnetic field from a magneto-optical trap

We study a Zeeman slower using the magnetic field generated by a pair of coils for a magneto-optical trap. The efficiency of the Zeeman slower is shown to be dependent on the intensity and frequency detuning of the laser light for slowing the atoms. With the help of numerical analysis, optimal experimental parameters are explored.Experimentally, the optimal frequency detuning and intensity of the slowing beam are explored, and 4 × 10~7 ytterbium atoms are trapped in the magneto-optical trap.     

Field ionization of free helium atoms: Correlation between the kinetic energy of ionized atoms and probability of their field ionization

In this paper the correlation between the kinetic energy of helium atoms and the probability of field ionization is investigated by exploiting the narrow velocity distribution of supersonic molecular beams. Field ionization measurements were carried out on supersonic helium beams at 298 K and 95 K corresponding to energies of about 65 meV and 20 meV, respectively, for the individual atoms. The field ionization was performed with a tungsten tip, radius of curvature 12 nm, kept at room temperature. The ionization probability was found to increase by about a factor 10 when the beam was cooled from 298 K to 95 K. The results presented in this paper are of importance for improving the understanding of field ionization and for the development of a new detector for helium and other molecular beams.     

Orientation of aligned alkali atoms under magnetic resonance in a weak magnetic field

It is shown that, upon excitation of the magnetic resonance in a system of aligned atoms with unequally spaced sublevels, the atoms should become oriented. This orientation was detected experimentally for Cs atoms pumped by unpolarized light in the magnetic field of the Earth.     

Effect of a magnetic field on thermally stimulated ionization of impurity centers in semiconductors by submillimeter radiation

The probability of electron tunneling from a bound state into a free state in crossed ac electric and dc magnetic fields is calculated in the quasiclassical approximation. It is shown that a magnetic field decreases the electron tunneling probability. This decreases the probability of thermally activated ionization of deep impurity centers by submillimeter radiation. The logarithm of the ionization probability is a linear function of the squared amplitude of the electric field and increases rapidly with the frequency of the electric field.     

The ionization of atoms in an intense nonclassical electromagnetic field

The ionization of atoms in a strong nonclassical unimodal electromagnetic field was considered. It was shown that the probability of ionization could substantially change depending on the quantum state of the field even at a constant mean number of quanta in the radiation mode. The difference of ionization rates was especially large for multiphoton ionization processes. It was, in particular, shown that a nonclassical field could be much more effective from the point of view of the ionization of atoms than a classical field of the same intensity. The characteristics of the decay of a bound atomic system state in a strong nonclassical field were studied without invoking perturbation theory.     

Influence of Pauli exclusion principle on the strong field ionization of two electron atoms

We investigate the double ionization of helium under an intense laser pulse. This process is known to be one of the prototypical manifestation of electron–electron correlation. In this work, we present a numerical study on the influence of Paulis exclusion principle in the double ionization. We make a comparative analysis of two almost degenerated states with different character with respect to the exchange symmetry. We show that there exists a significant difference in the double ionization of parahelium and orthohelium. The symmetric character of the spatial electronic wavefunction affects strongly double ionization. It is found that the double ionization is partially suppressed in the orthohelium case. The mechanisms relevant for this suppression are discussed. PACS 31.15.Ar; 31.25.Jf     

Effect of polarization spectroscopy in multitep excitation and ionization of atoms on ionization efficiency

In this peper, the seventeen real motion equation of atoms were shown for the first time inconsiderlng the polarization choices of laser lights. The importance of polarization spectrcoscopy in thedetermination of ionization yields of multi-step excitation and ionization of atoms (MSEIA) wasshown.     

Effect of external magnetic field on the shift of resonant frequency in photoassociation of ultracold Cs atoms

We study the influence of external magnetic field on the shift of the resonant frequency in the photoassociation of ultracold Cs atoms, which are captured in a magnetically levitated optical crossed dipole trap. With the increase of the photoassociation laser intensity, the linear variation of the frequency shift is measured by recording the photoassociation spectra of the long-range 0_u~+ state of Cs molecule below the 6S_(1/2)+ 6P_(1/2) dissociation limit at different magnetic fields.The slope of the frequency shift to the intensity of the photoassociation laser exhibits a strong dependence on the external magnetic field. The experimental data is simulated with an analytic theory model, in which a single channel rectangular potential with the tunable well depth is introduced to acquire the influence of the magnetic field on the atomic behavior in the effective range where photoassociation occurs.