E. Matthias

Changes in nuclear mean square charge radii of stable Krypton isotopes

The isotope shifts of stable even Kr isotopes (A=78 throughA=86) in the optical transitions at 432 nm and 557 nm were measured by means of polarization laser spectroscopy. The observed shifts are consistent with earlier results for other transitions. From the isotope shifts the changes in the nuclear mean square charge radiiδ〈r2〉 were inferred using preliminary muonic isotope shift data. Starting from78Kr, a monotonic decrease of 〈r2〉 with increasing mass number is found throughout theg9/2 neutron shell. The effect onδ〈r2〉 of nuclear deformations as well as possible contributions due to changes in the skin thickness of the nuclear charge distribution are discussed.

Influence of atomic alignment on crossover signals in saturation spectroscopy

The crossover resonance between the atomic transitions2S1/2(F=2)→2P1/2(F′=1, 2), observed in the saturation spectrum of sodium, was found to be sensitive to the atomic orientation of the ground state, produced by velocity selective optical pumping. For zero magnetic field and the same linear polarization of saturating and probing beam, a negative signal was recorded for the crossover, corresponding to an increase in absorption of the probing beam. Application of a sufficiently strong magnetic field perpendicular to the polarization vector causes the destruction of the alignment, leading to a change in sign for the crossover intensity, i.e., to an enhanced transmission of the probing beam. It was shown experimentally that an increase in the atomic transit time has the same effect. Using optical pumping theory all qualitative features could be accounted for.

Isotope shifts and hyperfine structure of the 6s-7p transitions in the cesium isotopes 133, 135, and 137

The 6s-7p transitions in cesium at 459.3 nm (72P1/2) and 455.5 nm (72P3/2) have been investigated by saturation spectroscopy in vapor cells, using a laser spectrometer with 500 kHz bandwidth in the blue spectral range. Isotope shifts as well as hyperfine splittings were determined for the isotopes 133, 135 and 137.

Frequency modulation of the 6.2 keV Mssbauer states of181Ta

Mössbauer sidebands up to the first order from a single parent line have been produced by subjecting a non magnetic W(181W) Mössbauer source to a strong oscillating magnetic field of up to 230 Oe amplitude and a frequency of about one megahertz. The sidebands positions and intensities agree very well with theory, which is based on a periodic time-dependent interaction of the magnetic field with the nuclear magnetic moments of ground and excited states, respectively. From the sideband intensity ag-factor ratio ofge/gg=1.75(6) was derived.

Isotope shifts of perturbed 6sns1S0 and3S1 Rydberg states of odd barium isotopes

Isotope shifts of the pairs Ba 135–138 and 137–138 have been measured for the 6sns1S0 (11≦n≦23) and 6sns3S1 (14≦n≦23) Rydberg states. A quantitative analysis of the data in terms of hyperfine-induced singlet-triplet mixing was carried out. Admixtures of local perturbers belonging to the 5d 7d configuration were easily identified and admixture coefficients were derived.

Odd-even staggering of isotope shifts in the5sns 1S0 Rydberg series of strontium

High resolution two-photon spectroscopy was applied to investigate isotope shifts of Ssns S0 Rydberg states of natural strontium in the range 10 ≤ n ≤ 70. While the isotope shifts between the even isotopes 84, 86, and 88 showed no change, a dramatic increase of the shift with increasing principal quantum number was found for the odd isotope Sr-87.

Subshell effect in mean square charge radii of stable even cadmium isotopes

Isotope shifts of the 467.8 nm line have been measured by Doppler-free saturation spectroscopy for the even Cd isotopes 106 through 116. The differential changes in mean square charge radii derived from the field shifts show a pronounced break in their trend atN=64, giving evidence for the closure of theg7/2 neutron subshell. The average charge radii determined from our data and the rms radius of114Cd measured with muonic X-rays verify the general trend predicted by the droplet model but are off by about 35 mfm on an absolute scale. A consistent interpretation of δ〈r2〉 further supports the necessity for considering changes in the skin thickness of the nuclear charge distribution.

The magnetic moment of the first 2+ state in22Ne

Theg-factor of the 1,275 keV 2+ state in22Ne has been measured by means of the time-differential recoil-into-vacuum (plunger) technique. An analysis including excited heliumlike electronic configuration was performed. A fit, which includes all these electronic states, provides a value of ¦g¦=0.36±0.03.

Hyperfine Structure and Isotope Shifts of Rydberg States in Alkaline Earth Atoms

Rydberg states of atoms with two valence electrons exhibit three markedly different features compared to alkali systems. First of all, the coupling between the two valence electrons is most crucial for the properties of the Rydberg states and, in general, we have to distinguish between series with predominant singlet or triplet character. Secondly, low-lying states of doubly excited configurations cause strong perturbations of the Rydberg series belonging to one excited valence electron. This can lead to both singlet-triplet mixing and/or configuration mixing more or less local in energy. The third feature involves the interaction between the ms valence electron of the ion and the nucleus. The electro-static part of it reveals itself through the field shift, while for nuclei with I=0 the magnetic interaction causes a hyperfine splitting as well as a higher-order shift.

Further evidence for a linear relationship between changes in nuclear charge radii and binding energies per nucleon

The comparison of precise isotope shift data of Xe and Ba with the corresponding changes in binding energy per nucleon reveals a linear relationship between Δ and Δ(B/A) for even-even nuclei throughout the h11/2 neutron shell. The last pair, involving the magic neutron number, is an exception to this rule, indicating the existence of a shell-closure effect.