P. Grundevik

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.

Hyperfine structure in the 6p5d configuration and isotope shifts in transitions between the 6s5d and the 6p5d configurations in Ba I

High-resolution laser fluorescence spectroscopy, using a single-mode dye laser acting on a collimated atomic beam, has been performed to determine the hyperfine-structure (hfs) constants in six states of the 6p 5d configuration of135Ba and137Ba. Isotope shifts (IS) for eleven transitions between the 6s 5d and the 6p 5d configurations have also been measured. From an analysis of the energy levels, intermediate angular wavefunctions have been deduced. The wavefunctions are used to evaluate experimental hyperfine parameters from the experimental hfs constants. The parameters are, for the magnetic-dipole interaction compared with theoretical values, and for the electricquadrupole interaction used to estimate the nuclear quadrupole moments for the odd isotopes.The IS in the measured transitions are analysed using a King-plot, with the first resonance line in Ba II as the reference. Specific mass and field shifts are evaluated for the measured transitions. The field shifts have been used to determine the change in mean-square radius between the natural abundant Ba-isotopes.

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.

High resolution laser fluorescence spectroscopy in the deep blue spectral region

High-resolution laser spectroscopy measurements have been performed in the wavelength region around 4000 Å using a pulsed dye laser acting on a collimated atomic beam. Extra-cavity Fabry-Pérot filtering was used to achieve a narrow line-width of the laser light. Isotope shifts were measured in the 4216 Å and 4202 Å rubidium lines with the result Δσ(87, 85)=124.3(4)MHz, andΔσ(87, 85) = 124.2(7)MHz, respectively, and in the 3988 Å ytterbium line with the resultδσ(176, 174)=−509(4)MHz, Δσ(174, 172)=−530(4) MHz.

Isotope shifts in dysprosium measured by high resolution laser spectroscopy

Using a pulsed dye laser, acting on a collimated atomic beam, the isotope shifts between the dysprosium isotopes 164, 162, and 160 were measured with high precision in three lines, , and 5652 A.

Hyperfine-structure study in the P sequence of 23 Na using quantum-beam spectroscopy

Describes use of the quantum-beat method to study hyperfine structure in the 52P3/2 and 62P3/2 states of 23Na. A pulsed dye laser, frequency-doubled into the UV region, was used to excite sodium atoms abruptly in a beam. The fluorescent light was recorded with a fast transient digitiser, interfaced to a micro-computer. Theoretical calculations using many-body perturbation theory were performed for the entire P sequence measured so far, taking polarisation and correlation effects into account separately. Very good agreement between experimental and theoretical values was obtained.

Analysis of the isotope shifts and hyperfine structure in the 3 988 Å (6s6p1P1↔6s21S0) YbI line

High-resolution laser spectroscopy using a pulsed dye-laser acting on a collimated atomic beam has been used to determine the isotope shifts in the 3 988 Å YbI line. The following results have been obtained:Δσ(176, 174)=−509(4)MHz,Δσ (174, 173)=−291(10) MHz,Δσ(174, 172)=−530(4) MHz,Δσ(172, 171)=−414(5) MHz andΔσ(172, 170)= −665(10) MHz. The sign of the magnetic dipole interaction constant in the1P1 state for171Yb is found to be negative,a(1P1, 171)=−213.4(3.0) MHz. The electric quadrupole interaction constant for173Yb in the1P1 state is found to beb(1P1, 173)=605(20) MHz.

Measurement of the hyperfine structure splitting for the 4 and 5^(2)P_(1/2) states of sodium using radio-frequency spectroscopy

The hyperfine-structure splitting for the 4 and 52P1/2 states of sodium was measured using step-wise laser excitation combined with rf-resonance techniques. The magnetic dipole interaction constants were found to be a(42P1/2)=30.4(5) MHz and a(52P1/2) =13.3(2) MHz. The results are compared with a theoretical calculation, taking polarization effects into account.

Atomic-Beam and Resonance Spectroscopy of Alkali and Alkaline-Earth Atoms

During the last few years an extensive program of laser-spectroscopy investigations for sequences of alkali atomic states has been pursued in our laboratory. Very recently two fine-structure investigations were completed. The interesting Cs F-sequence was studied for n = 10−17 in experiments on a collimated beam [1]. With a CW dye laser the 7 2P3/2 state was excited, from which about 10 per cent of the atoms cascade to the 5 2D5/2 state. A single-mode, electronically tunable laser was then used to scan the 5 2D5/2 — n 2F7/2,5/2 transitions. The fine-structure, that is inverted for all the studied F states, can be expressed as an expansion in odd powers of the effective principal quantum number. In addition to collimated-beam measurements, prcision level-crossing determinations of the fine structure for the 5 and 6 2D K states were performed in a strong external magnetic field [2]. Also using precision values for high-n states, obtained by Gallagher and Cooke [3], an accurate expansion describing the K fine-structure splittings was determined.