Optical laser spectroscopy and hyperfine structure investigation of the 10²S, 11²S, 8²D, and 9²D excited levels in francium

Abstract

We present here an extension to low-lying states of francium (lOs, 1 Is, 8d, 9d) of a previously published high-resolution experiment performed on the ns and nd Rydberg levels. These four levels were investigated at CERN with the on-line mass separator ISOLDE using stepwise laser excitation in collinear geometry. Accurate energy measurements lead to a more reliable determination of the quantum defects of the whole ns and nd series, together with the ionization potential for 2'2Fr (nuclear spin I = 5 ) which is found to be 32 848.872 (9) cm-'. The measurement of the fine structure splittings for the nd 2D3,2,5,2 doublets has been completed at the same time. The main result of this study is the first observation and measurement of hyperfine structures in ' S and 'D states. Dipolar hyperfine constants deduced from hyperfine splittings are as follows: A(102S,,,) = 401 (5) MHz; A(S2D,,,) = -7.2 ( 6 ) MHz and A(9,DS,,) = -3.6 (4) MHz. The negative sign of the A(n2Dslz)/A(n2D5,?) ratios is a clear indication of the large core polarization effects as already pointed out in the case of other heavy alkali elements. A survey of all the available energy terms is also given to summarize the current knowledge of the francium optical spectrum.A(112S,,2) =225 ( 3 ) MHz;A(S2D3,2) = 13.0 (6) MHz; A(92D3,2) ~7 . 1 (7) MHz;

Correlation trends in the hyperfine structures ofFr210,212

“…Extra and norm correspond to contributions from the non-linear terms of the CCSD method that are not mentioned explicitly and corrections due to the normalization of the wave functions respectively. [16], which are also given in Table VIII. It can be seen that these results and our calculations agree very well.…”

“…To draw meaningful conclusions and to be consistent in the findings from comparisons between the theoretical and experimental hyperfine structure constants of different states, it is necessary to consider the results for as many as states as possible for both the isotopes. The second, but the essential reason behind considering the above two isotopes is that experimental results of hyperfine structure constants for only a few selective low-lying states of 210 Fr [12][13][14][15] and some other excited states of 212 Fr are available [16].…”

Radiative and correlation effects on the parity-nonconserving transition amplitude in heavy alkali-metal atoms

“…The infrared divergences, which occur in contributions (35)- (38) and (45)- (46), are regularized by introducing a nonzero photon mass and cancelled analytically.…”

“…The corresponding comparision for the francium atom, where the local potential was derived using mainly the DF wave function of the 7s state, is presented in Table II. Table III. Since there is a significant cancellation between terms containing the infrared singularities, the terms corresponding to n = a in Σ ′ R (ε a ) and n = b in Σ ′ R (ε a ) are subtracted from contributions (35)- (38) and added to contributions (45)- (46). The total SE correction δE tot PNC , presented in Table III, contains also the free term, −α/(2π)E PNC , mentioned above.…”

Laser cooling and trapping of neutral atoms

“…Its longest lived isotope has a half-life of 22 minutes. Previously, experiments to study the atomic structure of francium were possible only with the very high fluxes available at a few facilities in the world [40], or by use of natural sources [41].…”