Analog states of ¹⁴⁰La levels

Abstract

Analog states in ¹⁴⁰Ce have been studied through elastic and inelastic proton scattering on ¹³⁹La in the energy range E_p = 9–12 MeV. We have shown that the 14 first excited states of ¹⁴⁰La can be described by the two configurations [$\text{(}\text{g}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>p</mtext>}}\text{⊗ (}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>n</mtext>}}$] and [$\text{(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>p</mtext>}}\text{⊗ (}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>n</mtext>}}$] according to the assumption of Kern et al. The elastic scattering results are in complete agreement with the ¹³⁹La(d, p) ones. The study of the inelastic scattering to the 166 keV excited state of ${}^{139}\text{La}\text{(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{level}\text{)}$, which gives a direct and sensitive test of the [$\text{(}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>p</mtext>}}\text{⊗ (}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{<mtext>n</mtext>}}$] components, has confirmed that only these two configurations are important and that the relative intensities of the two configurations deduced from (d, p) experiments are correct. On the other hand, the two sets of theoretical wave functions which exist are not able to reproduce experimental results. We are able to confirm that the proton peak observed at E_p = 10.3 MeV in the ¹⁴⁰Ce(e, e'p)¹³⁹La reaction by Shoda et al. corresponds to the analog of the 1⁻ state at 466 keV in ¹⁴⁰La.