New recommended $\omega \gamma$ for the $E_r^{\mathrm{c}.\mathrm{m}.}=458$ keV resonance in ${}^{22}\mathrm{Ne}\left(p,\gamma \right){}^{23}\mathrm{Na}$

The $E_r^{\mathrm{c.m.}}=458$ keV resonance in ${}^{22}\mathrm{Ne}\left(p,\gamma \right){}^{23}\mathrm{Na}$ is an ideal reference resonance for measurements of cross sections and resonance strengths in noble gas targets. We report on a new measurement of the strength of this resonance. Data analysis employed the TFractionFitter class of root combined with geant simulations of potential decay cascades from this resonance. This approach allowed us to extract precise primary branching ratios for decays from the resonant state, including a new primary branch to the 7082-keV state in ${}^{23}\mathrm{Na}$. Our new resonance strength of $\omega \gamma$(458 keV) = 0.583(43) eV is more than $1\sigma$ higher than a recent high-precision result that relied on literature branching ratios.

Figure 1

The result of the best fit, shown in green, to experimental data on the 458-keV resonance in the ${}^{22}\mathrm{Ne}\left(p,\gamma \right){}^{23}\mathrm{Na}$ reaction, shown in black, as derived using the TFractionFitter [8] class of root [9] and the methodology detailed in the text and in Ref. [15]. Note that the data and fit result are nearly identical. Resonance primary peaks are indicated by blue arrows. The fit was derived considering geant [7] simulations of each potential decay cascade from the $J_R=1/29252$-keV resonant state in ${}^{23}\mathrm{Na}$ excited by this resonance to all lower lying states with $J=1/2$, 3/2, or 5/2. Only those with nonzero contributions were kept for the fit shown here. The two highest branching ratio templates and the room background template (blue and red, respectively) are shown as well. Note that these spectra have a lower number of counts. A total of eight other decay cascade templates were used for the fit shown here. Branching ratios were derived using the relative contributions of these simulations and are shown in Table 1.

Figure 2

The experimental yield from the $E_r^{\mathrm{c}.\mathrm{m}.}=458$ keV resonance from the 6270- and 2170-keV $\gamma$ rays observed in this work, shown as black circles and red (gray) diamonds, respectively. The yield scale for data points of either color is given by the $y$ axis of the same color. The 2170-keV $\gamma$ ray corresponds to a new primary transition, first identified in this work, to the 7082-keV state in ${}^{23}\mathrm{Na}$ while the 6270-keV $\gamma$ ray corresponds to the well-known $R\to 2982$ transition. Definitive identification of the 2170-keV $\gamma$ ray as a resonant state decay in ${}^{23}\mathrm{Na}$ is provided by the similarity between the measured yield of these two $\gamma$ rays.

Figure 3

A plot of $Y_j$, the experimental yield from the $E_r^{\mathrm{c.m.}}=458$ keV resonance in the ${}^{22}\mathrm{Ne}\left(p,\gamma \right){}^{23}\mathrm{Na}$ reaction, for all primary $\gamma$-ray transition peaks. The $Y_j$ values calculated using the branching ratios of Piiparinen et al. [3] are shown as squares, those using Meyer et al. [4] are shown as open circles, and those using the present branching ratios are shown as diamonds. The dashed line at $Y_j=1$ is shown to help guide the eye, while the dashed lines above and below $Y_j=1$ represent a factor of 2 and 3 deviation from $Y_j=1$. The geometric standard deviation, ${\sigma }^{\mathrm{geo}}$, of each data set is shown as well. See text for a discussion of the data shown here.

Figure 4

Full-energy peak efficiencies of the 135% HPGe detector used in this work derived from data on the $E_r^{\mathrm{c.m.}}=259$ keV resonance in the ${}^{14}\mathrm{N}\left(p,\gamma \right){}^{15}\mathrm{O}$ reaction. Data were taken with 0, 5, 10, and 20 cm added to the minimum source-to-detector distance of 1.1 cm, shown above as the diamond, square, circle, and cross data points, respectively. Data that were sum corrected (SC) and data that were not sum corrected (NSC) are shown as solid and open data points, respectively. Dashed lines represent the expected full-energy peak efficiency curve of the HPGe detector at each source-to-detector distance, each of which have been scaled to include an independent, experimental peak efficiency measurement at 1333 keV. In general, agreement is achieved between the sum-corrected data and the expected peak efficiency curve at each distance.