CI-MBPT and Intensity-Based Lifetime Calculations for Th II

Savukov, Igor M.

doi:10.3390/atoms8040087

CI-MBPT and Intensity-Based Lifetime Calculations for Th II

Journal Article · Tue Dec 01 00:00:00 EST 2020 · Atoms

DOI:https://doi.org/10.3390/atoms8040087· OSTI ID:2396029

Lifetime calculations of Th II J = 1.5 and 2.5 odd states are performed with configuration–interaction many-body perturbation theory (CI-MBPT). For many J = 2.5 states, lifetimes are quite accurate, but two pairs of J = 2.5 odd states and many groups of J = 1.5 states are strongly mixed, making theoretical predictions unreliable. To solve this problem, a method based on intensities is used. To relate experimental intensities to lifetimes, two parameters, one an overall coefficient of proportionality for transition rates and one temperature of the Boltzmann distribution of populations, are introduced and fitted to minimize the deviation between theoretical and intensity-derived lifetimes. For strongly mixed groups of states, the averaged lifetimes obtained from averaged transition rates were used instead of individual lifetimes in the fit. Close agreement is obtained. Then intensity branching ratios are used to extract individual lifetimes for the strongly mixed states. The resulting lifetimes are compared to available directly measured lifetimes and reasonable agreement is found, considering limited accuracy of intensity measurements. The method of intensity-based lifetime calculations with fit to theoretical lifetimes is quite general and can be applied to many complex atoms where strong mixing between multiple states exists.

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Research Organization:: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Organization:: USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: 89233218CNA000001

OSTI ID:: 2396029

Alternate ID(s):: OSTI ID: 1807848

Report Number(s):: LA-UR--20-28610; PII: atoms8040087

Journal Information:: Atoms, Journal Name: Atoms Journal Issue: 4 Vol. 8; ISSN 2218-2004; ISSN ATOMC5

Publisher:: MDPI AGCopyright Statement

Country of Publication:: Switzerland

Language:: English

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