Information on Nuclear Quadrupole Moments from Laser-rf Double-Resonance Spectroscopy

Abstract

The determination of nuclear quadrupole moments of stable nuclei from the hyperfine structure (hfs) of atomic spectra is still a challenge to atomic physics mainly for three reasons: 1) The nuclear quadrupole moment Q cannot be determined directly from hyperfine structure measurements, but only the quadrupole interaction constant B, which contains relativistic and configuration interaction effects including the Sternheimer quadrupole shielding and antishielding. This limits in many cases the accuracy, with which Q can be determined from such measurements, the uncertainty for Q beeing typically of the order of 10...20% or even bigger. 2) There are some very rare isotopes, for which the quadrupole interaction could not be measured in the past, because the resonance signals of all methods used so far were too low for detection. 3) For some isotopes the hyperfine structure could be measured only in atomic ground states, which have no gradient of the electric field and thus have no quadrupole interaction. — For all three cases the laser-rf double-resonance spectroscopy with the ABMR-LIRF method (atomic beam magnetic resonance, detected by laser induced resonance fluorescence) has brought considerable progress recently, which will be reported here with three examples. The method itself, which was developed in our laboratory in Bonn by ERTMER and HOFER [1] and at the same time independently for molecular beam magnetic resonance at London (Ontario) in Canada by ROSNER, HOLT and GAILY [2], is described in detail in the next paper of this volume by CHILDS, GOODMAN and POULSEN, and the description will therefore be omitted here.