New levels and a lifetime measurement inTl202

Abstract

The $^{203}\mathrm{Tl}$($n,2n\ensuremath{\gamma}$) reaction was used to study excited states in $^{202}\mathrm{Tl}$. The data were taken using the GEANIE spectrometer. The pulsed neutron source of the Los Alamos Neutron Science Center's WNR facility provided neutrons in the energy range from 0.6 to 250 MeV. The time-of-flight technique was used to determine the incident neutron energies. \ensuremath{\gamma}-ray excitation functions were measured from the beam-on data, whereas half-lives of isomers were determined from the beam-off data. The level scheme of $^{202}\mathrm{Tl}$ has been considerably enriched and the low-spin part of the level scheme exhibits striking similarities to that of the neighboring $^{204}\mathrm{Tl}$ isotope. The previously reported first excited state in $^{202}\mathrm{Tl}$ has been decomposed into two close-lying states in the present measurement. The half-life of the ${7}^{+}$ isomer at 950-keV excitation energy was measured with a more precise result that differs by \ensuremath{\sim}4% from the value adopted in the literature.