Photoneutron cross sections for ${}^{96}\mathrm{Zr}$: A systematic experimental study of photoneutron and radiative neutron capture cross sections for zirconium isotopes

Photoneutron cross sections were measured for ${}^{96}\mathrm{Zr}$ near neutron threshold with quasimonochromatic laser-Compton-scattering $\gamma$-ray beams. A systematic analysis of photoneutron and radiative neutron capture data for zirconium isotopes within the statistical model calculation leads to a unified picture of low-energy $\gamma$-ray strengths for zirconium isotopes that is described by the HFB $+$ QRPA model of $E1$ strength supplemented with an extra $\gamma$ strength attributed to a giant $M1$ resonance. Results of the systematic analysis including radiative neutron capture cross sections for radioactive ${}^{95}\mathrm{Zr}$ and ${}^{93}\mathrm{Zr}$ nuclei are presented.

Figure 1

An energy spectrum of the LCS $\gamma$-ray beam measured with the high-resolution high-energy photon spectrometer (solid line) and its unfolded spectrum (dotted line).

Figure 2

Comparison of experimental and theoretical ${}^{96}\mathrm{Zr}$($\gamma$,$n){}^{95}\mathrm{Zr}$ cross sections. The solid (dotted) line corresponds to the QRPA calculation with (without) the $M1$ component, as discussed in the text. The dash-dot line is obtained with a pure Lorentzian model. The diamonds corresponds to the cross section recommended by the IAEA handbook [14].

Figure 3

Comparison of experimental and theoretical ${}^{90}\mathrm{Zr}$($n,\gamma$)${}^{91}\mathrm{Zr}$ cross sections. The theoretical curves were obtained with the $E1$ HFB + QRPA strength [16] supplemented with a strong $M1$ resonance as well as with the standard Lorentzian for both the $E1$ and $M1$ strengths, as recommended in Ref. [17]. The error bars on the theoretical estimate are obtained using different nuclear level-density prescriptions. The experimental data are from Refs. [18, 19, 20].

Figure 4

Same as Fig. 3 for ${}^{91}\mathrm{Zr}$($n,\gamma$)${}^{92}\mathrm{Zr}$. Experimental data are taken from Refs. [18, 21, 22].

Figure 5

Same as Fig. 3 for ${}^{92}\mathrm{Zr}$($n,\gamma$)${}^{93}\mathrm{Zr}$. Experimental data are taken from Refs. [19, 21].

Figure 6

Same as Fig. 3 for ${}^{93}\mathrm{Zr}$($n,\gamma$)${}^{94}\mathrm{Zr}$. Experimental data are taken from Ref. [23].

Figure 7

Same as Fig. 3 for ${}^{94}\mathrm{Zr}$($n,\gamma$)${}^{95}\mathrm{Zr}$. Experimental data are taken from Refs. [18, 19, 26, 27].

Figure 8

Same as Fig. 3 for ${}^{96}\mathrm{Zr}$($n,\gamma$)${}^{97}\mathrm{Zr}$. Experimental data are taken from [19, 26, 28, 29].

Figure 9

Same as Fig. 3 for ${}^{95}\mathrm{Zr}$($n,\gamma$)${}^{96}\mathrm{Zr}$. The HFB + QRPA ${}^{96}\mathrm{Zr}$ $\gamma$-ray strength is constrained by the photoneutron data given in Fig. 2.