Time-dependent quantum wave packet calculations were carried out for the F ＋ HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabi...Time-dependent quantum wave packet calculations were carried out for the F ＋ HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabilities dramatically increase near the zero collision energy and then slightly decrease with increasing collision energy, which corresponds well to the behavior of a barrierless reaction. The effects of reagent HBr excitation were examined, it is shown that both the vibrational and the rotational excitations of reagent HBr have a negative effect on the reactivity of F ＋ HBr. The integral cross-section for the ground state of the reagent HBr decreases at a low collision energy and then becomes plat with increasing collision energy, which is reasonable for the feasibility of such an exothermal reaction. The rate constant that was obtained is slightly higher than that obtained in the quasi-classical trajectory calculation.展开更多
The thermonuclear^19F（p,α0）16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolation...The thermonuclear^19F（p,α0）16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolations.Our new rate deviates by up to about 30% compared to the previous results, although all rates are consistent within the uncertainties. At very low temperature（e.g. 0.01 GK） our reaction rate is about 20% lower than the most recently published rate, because of a difference in the low energy extrapolated S-factor and a more accurate estimate of the reduced mass used in the calculation of the reaction rate. At temperatures above ^1 GK, our rate is lower, for instance, by about 20% around 1.75 GK, because we have re-evaluated the previous data（Isoya et al., Nucl. Phys.7, 116（1958）） in a meticulous way. The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20% in the temperature region below 0.2 GK,and are mainly caused by the lack of low-energy experimental data and the large uncertainties in the existing data.Asymptotic giant branch（AGB） stars evolve at temperatures below 0.2 GK, where the^19F（p,α）16O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, the fluorine over-abundances observed in AGB stars. Precise cross section（or S factor） data in the low energy region are therefore needed for astrophysical nucleosynthesis studies.展开更多
基金Supported by the Open Project Program of Key Laboratory of Advanced Materials &Rheological Properties, Ministry of Educa-tion, China(No KF0504)
文摘Time-dependent quantum wave packet calculations were carried out for the F ＋ HBr reaction on the latest London-Erying-Polanyi-Sato potential energy surface constructed by Persky et al. The calculated reaction probabilities dramatically increase near the zero collision energy and then slightly decrease with increasing collision energy, which corresponds well to the behavior of a barrierless reaction. The effects of reagent HBr excitation were examined, it is shown that both the vibrational and the rotational excitations of reagent HBr have a negative effect on the reactivity of F ＋ HBr. The integral cross-section for the ground state of the reagent HBr decreases at a low collision energy and then becomes plat with increasing collision energy, which is reasonable for the feasibility of such an exothermal reaction. The rate constant that was obtained is slightly higher than that obtained in the quasi-classical trajectory calculation.
基金Supported by National Natural Science Foundation of China(11490562,11490560,11675229)National Key Research and Development Program of China(2016YFA0400503)
文摘The thermonuclear^19F（p,α0）16O reaction rate in the temperature region 0.007–10 GK has been derived by re-evaluating the available experimental data, together with the low-energy theoretical R-matrix extrapolations.Our new rate deviates by up to about 30% compared to the previous results, although all rates are consistent within the uncertainties. At very low temperature（e.g. 0.01 GK） our reaction rate is about 20% lower than the most recently published rate, because of a difference in the low energy extrapolated S-factor and a more accurate estimate of the reduced mass used in the calculation of the reaction rate. At temperatures above ^1 GK, our rate is lower, for instance, by about 20% around 1.75 GK, because we have re-evaluated the previous data（Isoya et al., Nucl. Phys.7, 116（1958）） in a meticulous way. The present interpretation is supported by the direct experimental data. The uncertainties of the present evaluated rate are estimated to be about 20% in the temperature region below 0.2 GK,and are mainly caused by the lack of low-energy experimental data and the large uncertainties in the existing data.Asymptotic giant branch（AGB） stars evolve at temperatures below 0.2 GK, where the^19F（p,α）16O reaction may play a very important role. However, the current accuracy of the reaction rate is insufficient to help to describe, in a careful way, the fluorine over-abundances observed in AGB stars. Precise cross section（or S factor） data in the low energy region are therefore needed for astrophysical nucleosynthesis studies.
