Lifetimes of low-lying states in 19F

Abstract

Lifetimes of low-lying states in 19F were measured using the Doppler-shift attenuation method through the 15 N( α, γ) 19F reaction. Values of τ m = 3700 ± 700 fs (1.35 MeV), 140 ± 15 (1.46), 19 ± 7 (4.00) and 63 ± 19 (4.03) were obtained for the lowest 5 2 − , 3 2 − , 7 2 − and 9 2 − members, respectively, of the K π = 1 2 − rotational band and 5 ± 3 fs (1.55 MeV) and 370 ± 25 (2.78) for the 3 2 + and 9 2 + members of the K π = 1 2 + ground-state band. For the Doppler-shift attenuation analysis correction factors of the nuclear and electronic stopping powers were determined by measuring the Doppler-shift attenuation and γ-ray line shape of the 2.78 → 0.20 MeV transition and range values of 100, 200. 300 and 370 keV 19F nuclei in tantalum. All calculations were done with Monte Carlo methods. The transition strengths are discussed in terms of different theoretical predictions.