The influence of momentum diffusion on laser cooling of atoms

We show that laser cooling by coherent population trapping in case of zero radiation force — when atomic evolution is due to only momentum diffusion — can be effectively described by use of the Fokker-Planck equation for the atomic distribution function. Our quasiclassical approach allows numerically and analytically to investigate the dynamics and the efficiency of the cooling process. It is shown that both the evolution of the momentum distribution and the limit of the cooling are determined by the degree of incompleteness of coherent population trapping.     

Visible-laser-induced chemiluminescence of NaHg red excimer bands

Visible argon ion laser lines were used to induce the chemiluminescence of the NaHg excimer. Sodium dimers, excited into theB ¹Π _u state, produced in reactive collision with Hg atoms the NaHg excimers in the first excited electronic states. A qualitative analysis of the origin of the observed spectra, based on ab initio NaHg potential curves calculations, is presented.     

A new energy level of the neutral tantalum atom

Investigating the hyperfine structure (hfs) of the not yet classified line λ=4160.99 Å we succeeded in the determination of the electronic angular momenta of the combining levels and in the identification of the lower level using the hfs constants of all known levels as a finger-print card-index. In this way the lower level turned out to be thea ² G _9/2 level, which has even parity. Using the energy of this level and the wavenumber of the transition it was possible to determine the energy of the (odd parity) upper level to 34716.23 ± 0.02 cm^?1. The total angular momentum quantum number amounts toJ=11/2. Additionally, it was possible to identify the line λ=3436.00 Å as a further combination with this new level.     

Zeeman- and Paschen-Back-effect of the hyperfine structure of the sodiumD 2-line

Using high resolution laser-atomic-beam spectroscopy, Zeeman- and Paschen-Back-effects of the hyperfine structure of the sodium resonance lines were studied in magnetic fields up to 280 Gauss without perturbation by cross-over resonances. The observed behaviour of the components of theD ₂-line is compared with results of theoretical calculations for the splitting and the relative intensity of each Zeeman-component of the line. Full agreement between theory and experiment can be stated. Additionally, the relative intensities of the components of theD ₁-line are given.     

Fine-structure analysis of the (5d+6s)5 levels of Ta I

The fine structure of the prominent even levels of the neutral tantalum atom has been analyzed by simultaneous parametrization of one- and two-body interactions for the model space (5d+6s)⁵. The analysis was stimulated by the current discovery of several energy levels. It was possible to clear the configurations and designations of the energy levels given in commonly used tables. Magnetic-dipole hyperfine interaction constants A and electric-quadrupole hyperfine interaction constants B were calculated using the calculated eigenfunctions and adjusting radial integrals in a least-squares procedure which compares the calculated Aand B-constants with the experimental values. The rms error of this fitting procedure confirms the quality of the fine structure analysis. Moreover, wavenumbers and hyperfine constants of 52 further levels, up to now unidentified, are predicted.     

Investigations of the sodium and lithium D-lines in strong magnetic fields

Experimental and theoretical investigations of the splitting of the hyperfine structure of the sodium and lithium-D-lines in magnetic fields between 0 and 1 T were performed. In this magnetic field region the fine structure levelsJ=1/2 andJ=3/2 of the excited term² P begin to influence each other. In case of lithium crossings and anticrossings of hyperfine states stemming from different fine structure energy levelsJ=1/2 andJ=3/2 can be observed. The measurements were performed by laseratomic-beam spectroscopy in dependence on the applied external magnetic field strength. The experimental spectra were compared with computed spectra. Spectra were simulated by calculations using for the hyperfine hamiltonian two hyperfine constantsA andB in case of sodium and four hyperfine constantsa _c ,a _d ,a ₀ andb in case of lithium. Values for this constants could be derived by fitting the theoretical splittings to the experimental ones. For the first time theg _I — factor of sodium could be determined in a purely optical way.     

Investigation of the hyperfine structure of TaI-lines

The hyperfine structure of several spectral lines of the neutral tantalum atom was investigated by means of saturated optogalvanic laser spectroscopy. From the spectra, we have determined the magnetic hyperfine interaction constants A and the electric quadrupole interaction constants B of 14 levels with even parity and 23 levels of odd parity.     

Laser-spectroscopic investigations of the lithium resonance lines

High-resolution laser-atomic-beam spectroscopy allowed us to investigate the lithiumD lines in magnetic and electric fields and to determine hyperfine constants, isotope shifts, scalar and tensor polarizabilities and the absolute transition frequencies with high accuracy. The methods used are discussed and the results are summarized.     

Intensities of helium Stark lines in the region of levels anticrossing between n = 6 and n = 7

Studies of intensities of Stark lines of atomic He have been performed. The applied fields were high enough that shifts of the upper levels of the observed transitions became larger than the separation distance between levels with different principal quantum numbers. Overlapping of structures belonging to neighboring principal quantum numbers leads to levels anticrossing effects, what is reflected in variation of intensities of the observed spectral lines. Using the density matrix theory, calculations of the line intensities have been performed. By matching the superpositions of the excited states in the theoretical calculations we can follow the results of observation. Computer simulations have been performed for the observed levels anticrossing region between n = 6 and n = 7 in the second triplet series (2³P–n³Q, Q = S, P, D, ...).