Effect of 87Sr hyperfine structure on the isotopeselective excitation of 89Sr and 90Sr isotopes incollinear resonance ionization spectroscopy

Abstract

The 87Sr isotope has an extremely complex hyperfine structure(HFS) as a consequence of simultaneous mixing of the 3F2, 3F3, 3F4 and 1F3 fine structurecomponents in the 5s32f state. The resultant hyperfine spectrumof the 5s4d 3D3-5s32f 3F4 (364 nm)transition consists of 74 hyperfine components. HFSconstants A, B for both upper and lower levels havebeen derived from the single-electron contribution factors a5s, a4d3/2, a4d5/2, b4d3/2 and b4d5/2 using Breit-Wills formalism.Isotope ratio enhancement factors have been computed for the5s5p 3P2-5s21s 3S1 (325 nm),5s4d 3D3-5s32f 3F4 (364 nm) and the5s2 1S0-5s5p 3P1 (689.7 nm) transitions forisotope selective excitation/ionization of 89Sr and90Sr isotopes in collinear fashion. The results obtainedare comparable to that of the experimental results reported earlier. Simulations have been carried out for various laserlinewidths and acceleration potentials considering appropriateabundances, HFS of the odd isotope and massshifts of the constituent isotopes. This method can be used foroptimization of experimental configurations with respect toacceleration potentials and appropriate laser linewidths in orderto obtain better selectivities for the 89Sr and 90Srisotopes which allows the long term monitoring of theseisotopes in the environment. The present study shows that theHFS of the 87Sr isotope has a significanteffect on the isotope selective excitation of 89Sr and90Sr isotopes.