Ternary fission of ${}^{252}\mathrm{Cf}$: $3368\text{keV}$ $\gamma$ radiation from ${}^{10}\mathrm{Be}$ fragments

Ternary fission of ${}^{252}\mathrm{Cf}$ was studied at Gammasphere with eight $\Delta E\times E$ particle telescopes. After Doppler correction, the $3368\text{keV}{2}^{+}\to 0^{+}$ transition in ${}^{10}\mathrm{Be}$ was found in coincidence with the ${}^{10}\mathrm{Be}$ fragments with no evidence for any $\gamma$ rays not Doppler shifted for ${}^{10}\mathrm{Be}$ with $>21\text{MeV}$ kinetic energy. The ratio of the first $2^{+}$ to ground-state population probabilities was estimated as $N\left(2^{+}\right)∕N\left(0^{+}\right)=0.160\pm 0.025$. The angular distribution for $3368\text{keV}$ $\gamma$ rays indicated the spin alignment of excited ${}^{10}\mathrm{Be}$ nuclei preferentially is parallel or antiparallel to their momentum.

Figure 1

$\Delta E\times E$ plot. The data were collected by the first telescope during the whole time of the experiment. The $\Delta E$ and $E$ scales show just the values of energy deposited by the LCPs in the $\Delta E$ and $E$ detectors.

Figure 2

Energy distributions measured for the He, Be, B, and C LCPs. Closed circles show experimental data corrected for the energy losses in the source foils taking into account the energy losses in the $\Delta E$ detectors. Solid curves are Gaussian fits (see text).

Figure 3

Histograms drawn with the thin and thick solid lines, respectively, show the spectra of $\gamma$ rays coinciding with Be LCPs obtained before and after the Doppler shift correction. The dotted line shows the spectrum of $\gamma$ rays observed in coincidence with He LCP’s (see text).

Figure 4

Histogram drawn with a thick line shows the spectrum of $\gamma$ rays coinciding with Be LCPs. It is obtained from the thin solid line histogram of Fig. 3 after the subtraction of the background shown by the dotted line in Fig. 3. The thin line histogram demonstrates the spectrum simulated under the assumption of isotropic $\gamma$ emission from ${}^{10}\mathrm{Be}$. The second spectrum was normalized to the number of counts obtained in the first one in the energy range $3000–3800\text{keV}$.

Figure 5

Solid line histogram shows the spectrum of $\gamma$ rays detected at angles $<45°$ or $>135°$ to the Be momentum. The dotted line demonstrates the spectrum simulated with the same angular limitations, assuming isotropic $\gamma$ ray emission.

Figure 6

Angular distribution measured in the experiment for $3368\text{keV}$ $\gamma$ rays emitted by ${}^{10}\mathrm{Be}$ LCPs (solid line). $\theta$ is the angle between the ${}^{10}\mathrm{Be}$ momentum direction and the direction of $\gamma$ ray emission. Dashed line demonstrates the simulation made with the assumption of isotropic $\gamma$ ray emission from moving ${}^{10}\mathrm{Be}$ nuclei.