T. Olsson

High resolution laser spectroscopy of low-lyingp-states in Sr I and Ba I

Hyperfine structure and isotope shifts of the second excitedP states of Sr I and Ba I have been measured. In addition, the Sr I first resonance line has been studied.The present results are combined with existing data on both high-lying and lower-lying excited states, in a simple parametric study of the level isotope shifts in Sr I.

Hyperfine-structure and isotope-shift measurements in the 6s 5d↔6p 5d transitions of Ba I in the far-red spectral region

Measurements of the hyperfine structures in the 6p5d1D2,3D1 and3F2, 3, 4 states of135Ba and137Ba, and isotope-shifts in several far-red transitions between the 6s 5d and 6p 5d configurations, as well as the transition 6s21S0→6s6p3P1 at 7,911 Å have been performed using high-resolution laser spectroscopy on a collimated atomic beam of natural barium.An analysis of the magnetic-dipole interaction in the 6p 5d configuration using effective one- and two-body hyperfine operators is presented. In particular the contact interaction was studied with respect to the correlation between the two valence electrons. Effects of strong configuration interaction were found.From a King-plot analysis of the isotope shift term- andJ-dependence of the field shift have been evaluated for the transitions between the 6s 5d and 6p 5d configurations. Relativistic Hartree-Fock (RHF) calculations have been performed of electron densities at the nucleus for six different configurations in Ba I and Ba II. The RHF calculations reproduce the experimental King-plot slopes quite well, while the absolute values, of the changes in electron density at the nucleus for the studied transitions, are found to be 9% lower than the results derived from a muonic experiment.

Radio-frequency and laser spectroscopy studies of low-lying states in SrI

Precision hyperfine structure (hfs) measurements in the 5s4d1D2 metastable state of87Sr were performed using the laser radio-frequency double resonance method. The magnetic dipole and electric quadrupole interaction constants were found to bea=−5.5734(4) MHz andb=55.421(6) MHz. In addition high-resolution laser spectroscopy experiments were performed in the 5s4d1D2 ↔ 5s6p1P1 and 5s4d1D2 ↔ 5p4d1D2 transitions in SrI. The isotope shifts in the transitions and the hfs in the upper states were determined. Comparison of the experimental results with corresponding relativistic self-consistent-field (SCF) calculations shows that the states involved are very strongly perturbed. Therefore no reliable nuclear quadrupole moment for87Sr can be deduced from the data presented here without more detailed calculations. A relativistic SCF calculation of the electron density at the nucleus was used in combination with muonic values of the nuclear mean square radii to evaluate the field shifts. From the experimental isotope shifts the specific mass shifts in the two transitions can then be deduced. This shift was found to be particularly large in the transition 5s4d1D2 ↔ 5s6p1P1.

Analysis of the electronic structure, hyperfine structure, and volume isotope shifts in the low lying states of BA I and BA II

Relativistic multi-configuration Dirac Fock (MCDF) wavefunctions coupled to good angular momentum J have been calculated for low lying states of Ba I and Ba II. These wavefunctions are compared with semi-empirical ones derived from experimental atomic energy levels. It is found that significantly better agreement is obtained when close configurations are included in the MCDF wavefunctions. Calculations of the electronic part of the field isotope shift lead to very good agreement with electronic factors derived from experimental data. Furthermore, the slopes of the lines in a King plot analysis of many of the optical lines are predicted accurately by these calculations. However, the MCDF wavefunctions seem not to be of sufficient accuracy to give agreement with the experimental magnetic dipole and electric quadrupole hyperfine structure constants.

Laser and Radiofrequency Spectroscopy of the 4d55s 5D0,1,2,3,4 and 4d45s5p 5P1,2,3 States in Mo I: Hyperfine Structure and Isotope Shifts

A series of experiments has been performed to determine the hyperfine structure in the metastable 4d55s 5D1,2,3,4 states of Mo I by means of the laser radiofrequency double-resonance technique. Furthermore, hyperfine structure splittings and isotope shifts in seven optical transitions connecting the 4d55s 5D0,1,2,3,4 and the 4d45s5p 5P1,2,3 states were resolved with the high-resolution laser spectroscopy technique. Radial hyperfine structure parameters are deduced for the effective operator within the 5D states using the configuration 4d45s2, 4d55s and 4d6 as a model space. The isotope shifts are also discussed, utilizing an effective operator, with particular emphasis on the J dependence.

Laser and Radiofrequency Spectroscopy of the Hyperfine Structure in the 4d45s2 5D3,4 and 4d55p7P2,3,4 States in Mo I

The hyperfine structure and isotope shift in some weak, far-red transitions interconnecting the 4d45s2 5D and 4d55p 7P terms in Mo I were studied with high-resolution laser spectroscopy. Subsequently laser radio-frequency double-resonance experiments were performed in the two metastable states 5D3,4 in order to improve the accuracy of the hfs data obtained from the optical measurements. From the electric quadrupole interaction constants (corrected for hyperfine induced state mixing) the ratio between the quadrupole moments for the isotopes 97Mo and 95Mo was found to be Q(97)/Q(95) = -11.48(1) in good agreement with earlier works. The magnetic dipole interaction was analysed with an effective hfs operator technique and compared to relativistic Hartree-Fock calculations. Configuration mixing between the 4d45s2, 4d55s and 4d6 configurations was explicitly included in the angular wave-functions used in the analysis. In this way a major part of the two-body effects appearing in the effective hyperfine Hamiltonian could be explained.

State dependent volume isotope shift analysis of the low lying states of Ba I and Ba II.

Abstract Relativistic multi-configuration Dirac-Fock wavefunctions, coupled to good angular momentum J , have been calculated for low lying states of Ba I and Ba II. The resulting electronic factors show good agreement with data derived from recent high-resolution laser spectroscopy experiments and results from a comparison of muonic and optical data.

Laser amplified scintillations ? a method for new types of detectors?

A new method to obtain laser amplified scintillations (LAS) in Ne and other noble gases is presented and discussed. The Ne(2p53s) states populated by the ionizing radiation is repeatedly excited to the Ne(2p53p) states by resonant laser radiation and the subsequent fluorescent light is detected. The closed loop excitation-de-excitation process can give more than 10 photons/excited Ne(2p53s) atom. LAS applied in direct scintillation is expected to give the same energy resolution as that of proportional countrs. A new 3D track detector, with a recovery time of 10?s, is discussed. LAS can also be used to replace TEA and TMAE vapours in devices such as the parallel plate imaging chamber.