Measurement of the isotope shift and hyperfine structure splitting of Xe II by collinear fast ion beam laser spectroscopy

Abstract

The isotope shifts and hyperfine structure splittings of nine stable xenon isotopes in the mass range from 124 to 136 have been measured using the electronic transition 5d⁴D[subscript 7/2] - 6p⁴P⁰ [subscript 5/2] in the Xe II spectrum. The method of collinear fast ion beam laser spectroscopy has been utilized to achieve Doppler-free resolution and a high sensitivity. An ion beam apparatus consisting of an Einzel lens, a switch magnet and two electrostatic quadrupole triplets was designed to transport the ions from an on-line ion source through the TRISTAN isotope separator to the interaction region where, at resonance, the fluorescence signal was observed. A line shape analysis, based on an asymmetrical exponential function, was developed to interpret the recorded data. Changes in the mean square charge radii δ(r²)[superscript AA'] for the chain of stable xenon isotopes were extracted from the measured isotope shifts. The hyperfine structure constants A and B, the nuclear magnetic dipole moment μ[subscript I], and the electric quadrupole moment Q were evaluated from the splittings. The effect of the nuclear deformation below the magic number 82 is discussed in the two-parameter liquid drop model and the three-parameter droplet model. A comparison of the δ(r²)[superscript AA'] of Xe with those of the neighboring elements of Cs and Ba is made.