Proton emission from ${}^{125}\mathrm{Pm}$ could be observed

We perform a feasibility study for the search of proton decay from Pm, the last element without an isotope found, that decays by proton emission in the region of charges between 50 and 83. The behaviors of the half-lives for decay from the ground and possible isomeric states of ${}^{125}\mathrm{Pm}$ are discussed as a function of deformation, spin of the decaying state, and energy of the emitted proton, indicating the most probable regions of energy where proton radioactivity might be detected. We find that within our predictions, proton decay from ${}^{125}\mathrm{Pm}$ could be measurable.

Figure 1

Half-lives for emission of a proton from different spherical single-particle states in ${}^{125}\mathrm{Pm}$, as a function of the proton energy.

Figure 2

Experimental ground-state rotational bands of different Nd isotopes, compared to the negative-parity bands in the neighbor Pm nucleus. The quadrupole deformations ${\beta }_{GR}$ and ${\beta }_{MN}$ assigned to the different nuclei have been calculated using the Grodzins formula [16] and Möller and Nix predictions [11], respectively. The experimental data are taken from Refs. [17, 18, 19, 20, 21, 22, 23, 24].

Figure 3

Nilsson energy levels for protons in ${}^{125}\mathrm{Pm}$. The Fermi energy is represented by the green dot-dashed line.

Figure 4

Energies of the negative-parity states of the Hamiltonian of Eq. (1) with respect to the $J^{\pi }=11/2^{-}$ state for ${}^{131}\mathrm{Pm}$ and ${}^{133}\mathrm{Pm}$, as a function of deformation. The horizontal dashed lines indicate the experimental energies [18, 20], and the vertical ones indicate the deformation attributed in Ref. [16] (left) and Ref. [11] (right).

Figure 5

As in Fig. 4, for the positive-parity states in ${}^{133}\mathrm{Pm}$, with respect to the $J^{\pi }=3/2^{+}$ state.

Figure 6

Energy spectrum of the negative parity states of ${}^{125}\mathrm{Pm}$ with respect to the $J^{\pi }=11/2^{-}$ state, as a function of deformation.

Figure 7

As in Fig. 6 for the positive-parity states.

Figure 8

Energy difference between the $11/2^{-}$ and the $3/2^{+}$ states in ${}^{133}\mathrm{Pm}$ (red line) and ${}^{125}\mathrm{Pm}$ (green line). The dashed line indicates the experimental value for ${}^{133}\mathrm{Pm}$, and the arrows define the energy difference at the expected deformation predicted in Ref. [11].

Figure 9

$Q$ values of the proton emitters observed experimentally, and the mass formula predictions of Refs. [27, 28].

Figure 10

Half-lifes for decay from the states $3/2^{-}$, $5/2^{-}$, $7/2^{-}$, and $11/2^{-}$ at different proton energies.

Figure 11

Branching ratio for decay from different single-particle states, to the $2^{+}$ state in ${}^{124}\mathrm{Nd}$.

Figure 12

Half-life for decay of ${}^{125}\mathrm{Pm}$ from different single-particle states as a function of the proton energy, at a deformation $\beta =0.33$.