Evaluation of the K35(p,γ)Ca36 reaction rate using the

L. Lalanne¹,

O. Sorlin²,

M. Assié³

et al.

Abstract

Background: A recent sensitivity study has shown that the 35 K(p, γ) 36 Ca reaction is one of the ten (p, γ) reaction rates that could significantly impact the shape of the calculated X-ray burst light curve. Its reaction rate used up to now in type I X-ray burst calculations was estimated using an old measurement for the mass of 36 Ca and theoretical predictions for the partial decay widths of the first 2 + resonance with arbitrary uncertainties.Purpose: In this work, we propose to reinvestigate the 35 K(p, γ) 36 Ca reaction rate, as well as related uncertainties, by determining the energies and decay branching ratios of 36 Ca levels, within the Gamow window of X-ray burst, in the 0.5 to 2 GK temperature range.Method: These properties were studied by means of the one neutron pick-up transfer reaction 37 Ca(p, d) 36 Ca in inverse kinematics using a radioactive beam of 37 Ca at 48 MeV nucleon −1 . The experiment was performed at the GANIL facility using the liquid Hydrogen target CRYPTA, the MUST2 charged particle detector array for the detection of the light charged particles and a zero degree detection system for the outgoing heavy recoil nuclei. Results:The atomic mass of 36 Ca is confirmed and new resonances have been proposed together with their proton decay branching ratios. This spectroscopic information, used in combination with very recent theoretical predictions for the γ-decay width, were used to calculate the 35 K(p, γ) 36 Ca reaction rate. The recommended rate of the present work was obtain within a uncertainty factor of 2 at 1 sigma. This is consistent, with the previous estimate in the X-ray burst temperature range. A large increase of the reaction rate was found at higher temperatures due to two newly discovered resonances. Conclusions:The 35 K(p, γ) 36 Ca thermonuclear reaction rate is now well constrained by the present work in a broad range of temperatures covering those relevant to type I X-ray bursts. Our results show that the 35 K(p, γ) 36 Ca reaction does not affect the shape of the X-ray burst light curve, and that it can be removed from the list of the few influential proton radiative captures reactions having a strong impact on the light curve.

Enhancement and Saturation of Near-Field Radiative Heat Transfer in Nanogaps between Metallic Surfaces

“…Light particle identification was performed using the correlation between the energy loss, ΔE, and the residual energy, E, measured in the DSSSD and the CsI crystals, respectively (see Refs. [23,24] for more details).…”

“…Figure1(b) shows the one-proton energy reconstructed in the center of mass of36 Ca using the ðp; dÞ reaction with a gate on outgoing K only. Since the energy resolution reconstructed with the protons is better than with the deuterons ([23,24]), Fig.1(b) allows the determination of the energy peak centroids to be used for the fit of Fig.1(a) in the 4-5.5 MeV excitation energy range.The red lines in Figs.1(a)-1(d) display the best fits obtained using multiple Gaussian functions (shown with colored dotted lines) plus a small background contribution (green dashed line), generated by interactions of the beam particles with the windows of the LH 2 target, determined in a dedicated run with an empty target. The width of each peak used in the fit is constrained by simulations performed with the nptool package[25], the reliability of which is checked from the observed widths of isolated peaks [e.g., 0 þ 1 at 0 MeV in Fig.1(a) and 2 þ 1 at 3 MeV in Fig.1(b)].…”