Lifetime measurements of excited states in ${}^{57}\mathrm{Mn}$

Excited states in ${}^{57}\mathrm{Mn}$ are populated using the ${}^{55}\mathrm{Mn}({}^{18}\mathrm{O}$, ${}^{16}\mathrm{O}){}^{57}\mathrm{Mn}$ two-neutron transfer reaction at the FN tandem accelerator in Cologne. Lifetimes of excited nuclear states in ${}^{57}\mathrm{Mn}$ were determined utilizing the Doppler-shift attenuation method. A comparison between experiment and shell-model theory was made for excitation energies and reduced transition strengths along the odd-$Z$ isotopes Sc, V, Mn, and Co. The new results on transition strengths in ${}^{57}\mathrm{Mn}$ are described well by the standard interactions GXPF1A and KB3G. The development along the $N=32$ isotones for these odd-$Z$ nuclei and discrepancies between experiment and theory are discussed.

Figure 1

Particle-energy spectrum of the solar cells is shown with two dominant peaks coming from reactions with the Al backing and the Mn target. The chosen gate for the $\gamma$-particle coincidence analysis is indicated in red.

Figure 2

Partial level scheme of populated excited states in ${}^{57}\mathrm{Mn}$. The widths of the shown arrows correspond to the intensity of the transition adopted from Ref. [13]. Excitation energies and transition energies are given in keV. The analyzed transitions are marked in red.

Figure 3

$\gamma$-ray energy spectra for (a) forward and (b) backward angles are shown for the $11/2_1^{-}\to 7/2_1^{-}$ transition at 1144 keV. Spectra are produced by a gate on the two-neutron-transfer part in the particle spectrum. The final fit of the Doppler-broadened line shape is given in green. Additional contaminants are marked in orange and the background is given in blue lines. The convolution of all line-shape contributions is shown in red. See text for details.

Figure 4

$\gamma$-ray energy spectra for (a) forward and (b) backward angles are shown for the $9/2_1^{-}\to 7/2_1^{-}$ transition at 988 keV. The color code is similar to that of Fig. 3. Observed feeding contributions are given in purple.

Figure 5

Comparison between experimental and shell-model values for the odd-even Mn isotopes with neutron numbers $N=26$–36: (a) excitation energies $E_{9/2_1^{-}}$ of the $9/2_1^{-}$ state, (b) $B(E2;9/2_1^{-}\to 5/2_1^{-})$ values, and (c) $B(M1;9/2_1^{-}\to 7/2_1^{-})$ values. Adopted values (black triangles) from Ref. [11], the new results (red dots), and additional results (gray squares) obtained from Braunroth [29] are compared with the results of GXPF1A (blue dashed line) and KB3G (solid orange line) shell-model interactions.

Figure 6

Comparison between experimental and shell-model values for the odd-even Mn isotopes with neutron numbers $N=26$–36. (a) Excitation energies $E_{11/2_1^{-}}$ of the $11/2_1^{-}$ state and (b) $B(E2;11/2_1^{-}\to 7/2_1^{-})$ values. Same references and color code as in Fig. 5.

Figure 7

(a) Calculated and experimental excitation energies $E_{9/2_1^{-}}$ in keV for the $9/2_1^{-}$ state and (b) $B(E2;9/2_1^{-}\to 5/2_1^{-})$ values in W.u. (from Refs. [11, 29] and this work) for the odd-even Sc (squares), V (points), Mn (triangles), and Co (crosses) isotopes for neutron numbers $N=26$–36. The shell-model interaction GXPF1A (lines) is employed for the calculation.

Figure 8

(a) Calculated and experimental excitation energies $E_{11/2_1^{-}}$ in keV for the $11/2_1^{-}$ state and (b) $B(E2;11/2_1^{-}\to 7/2_1^{-})$ values in W.u. (from Refs. [11, 29] and this work) for the odd-even Sc (squares), V (points), Mn (triangles), and Co (crosses) isotopes for neutron numbers $N=26$–36. The shell-model interaction GXPF1A is employed for the calculation.