Isotope shift and hyperfine structure measurements on triple resonance excitation to the autoionizing Rydberg state of atomic strontium. (November 2021)

• Record Type: Journal Article
• Authors: Iwata, Yoshihiro; Miyabe, Masabumi; Akaoka, Katsuaki; Wakaida, Ikuo
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 275(2021)
• Publication Date: 2021-11
• Subjects: Strontium -- Resonance ionization -- Rydberg state -- Isotope shift -- Hyperfine structure -- King plot analysis; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2021.107882
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: Triple resonance excitation to the n e f f ∼ 39 Rydberg state (4d 2 D 3 / 2 series) of atomic Sr was studied using schemes (A) 689.4 nm-487.4 nm-393.8 nm and (B) 689.4 nm-472.4 nm-404.2 nm for the isotope-selective photoionization of 90 Sr. Isotope shifts and hyperfine structure constants of stable Sr isotopes were measured for the second and third transitions of schemes (A) and (B), most of which, to the best of our knowledge, have not been reported before or are more accurate than the values reported in the literature. The obtained 90 Sr level isotope shifts (LISs) of the neff ∼ 39 Rydberg state with respect to 88 Sr using schemes (A) and (B) show significantly negative values. This fact is important because a near-zero LIS causes a decrease in optical isotopic selectivity owing to the near-resonance transition. Our spectroscopic data will be useful in the future analysis of 90 Sr in real samples and may help promote studies in other fields, such as precision measurements using cold atoms in optical traps. Abstract: Triple resonance excitation to the autoionizing Rydberg state of atomic strontium was studied for the isotope-selective photoionization of strontium-90 ( 90 Sr). We investigated a new resonance ionization scheme, namely, 689.4 nm–472.4 nm–404.2 nm that is less affected by the multiphoton ionization induced by the first (689.4 nm) laser compared to the scheme in our previous study, namely, 689.4 nm–487.4 nm–393.8 nm. The isotope shifts and hyperfine structure constants of stable Sr isotopes were measured for the second and third transitions of these two schemes. Thus, the 90 Sr isotope shift for each of the four transitions was evaluated using the King plot analysis. Under the current laser conditions, no significant difference was observed in the measured 90 Sr optical isotopic selectivity between these two schemes, but the new scheme could show better selectivity if the first (689.4 nm) laser output is increased to improve the ionization efficiency. Our spectroscopic data will be useful for future analysis of 90 Sr in real samples and may also help promote studies in other fields, such as precision measurements using cold atoms in optical traps.