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Journal Articles

The $$^{59}$$Fe(n,$$gamma$$)$$^{60}$$Fe cross section from the surrogate ratio method and its effect on the $$^{60}$$Fe nucleosynthesis

Yan, S. Q.*; Li, X. Y.*; Nishio, Katsuhisa; Lugaro, M.*; Li, Z. H.*; Makii, Hiroyuki; Pignatari, M.*; Wang, Y. B.*; Orlandi, R.; Hirose, Kentaro; et al.

Astrophysical Journal, 919(2), p.84_1 - 84_7, 2021/10

 Times Cited Count:1 Percentile:11.19(Astronomy & Astrophysics)

Journal Articles

The $$^{95}$$Zr($$n, gamma$$)$$^{96}$$Zr cross section from the surrogate ratio method and its effect on $$s$$-process nucleosynthesis

Yan, S. Q.*; Li, Z. H.*; Wang, Y. B.*; Nishio, Katsuhisa; Lugaro, M.*; Karakas, A. I.*; Makii, Hiroyuki; Mohr, P.*; Su, J.*; Li, Y. J.*; et al.

Astrophysical Journal, 848(2), p.98_1 - 98_8, 2017/10

 Times Cited Count:5 Percentile:22.56(Astronomy & Astrophysics)

Journal Articles

Reanalysis of the ($$J$$ = 5) state at 592 keV in $$^{180}$$Ta and its role in the $$nu$$-process nucleosynthesis of $$^{180}$$Ta in supernovae

Hayakawa, Takehito; Mohr, P.*; Kajino, Toshitaka*; Chiba, Satoshi; Mathews, G. J.*

Physical Review C, 82(5), p.058801_1 - 058801_4, 2010/11

 Times Cited Count:14 Percentile:65.73(Physics, Nuclear)

We analyze the production and freeze-out of the isomer $$^{180}$$Ta in the $$nu$$-process. We consider the influence of a possible low-lying intermediate ($$J$$ = 5) state at 592 keV using a transition width estimated from the measured half-life. This more realistic width is much smaller than the previous estimate. We find that the 592 keV state leads only to a small reduction of the residual isomer ratio from the previous result. The isomer ratio changes from 0.39 to 0.38, whereas previously it was estimated that this transition could reduce the ratio to R = 0.18. This finding strengthens the evidence that $$^{138}$$La and $$^{180}$$Ta are coproduced by neutrino nucleosynthesis with an electron neutrino temperature of ${it kT}$ $$approx$$ 4 MeV.

Journal Articles

Photodisintegration cross section measurements on $$^{186}$$W, $$^{187}$$Re and $$^{188}$$Os; Implications for the Re-Os cosmochronology

Shizuma, Toshiyuki; Utsunomiya, Hiroaki*; Mohr, P.*; Hayakawa, Takehito; Goko, Shinji*; Makinaga, Ayano*; Akimune, Hidetoshi*; Yamagata, Tamio*; Ota, Masahisa*; Ogaki, Hideaki*; et al.

Physical Review C, 72(2), p.025808_1 - 025808_9, 2005/08

 Times Cited Count:41 Percentile:89.69(Physics, Nuclear)

Cross sections of the $$^{186}$$W, $$^{187}$$Re, $$^{188}$$Os($$gamma,n$$) reactions were measured using quasi-monochromatic photon beams from laser Compton scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are compared with the predictions of Hauser-Feshbach statistical calculations using four different sets of input parameters. In addition, the inverse neutron capture cross sections were evaluated by constraining the model parameters, especially the $$E1$$ strength function, on the basis of the experimental data. The present experiment helps to further constrain the correction factor $$F_{sigma}$$ for the neutron capture on the 9.75 keV state in $$^{187}$$Os. Implications of $$F_{sigma}$$ to the Re-Os cosmochronology are discussed with a focus on the uncertainty in the estimate of the age of the Galaxy.

Journal Articles

Photoneutron cross section measurements on $$^{186}$$W, $$^{187}$$Re and $$^{188}$$Os for cosmochronology

Shizuma, Toshiyuki; Utsunomiya, Hiroaki*; Goko, Shinji*; Mohr, P.*; Hayakawa, Takehito; Makinaga, Ayano*; Hara, Kaoru*; Ogaki, Hideaki*; Lui, Y.-W.*; Goriely, S.*

Nuclear Physics A, 758, p.561c - 564c, 2005/07

Photodisintegration experiments were carried out for $$^{186}$$W, $$^{187}$$Re, and $$^{188}$$Os using quasi-monochromatic $$gamma$$-ray beams from laser Compton scattering (LCS) at the National Institute of Advanced Industrial Science and Technology. The excitation function of ($$gamma$$,n) cross sections was measured for the three nuclei near neutron thresholds, taking advantage of the intense peaking of the energy-tunable LCS beam in the energy region of astrophysical importance. Neutron capture cross sections for $$^{185}$$W, $$^{186}$$Re, and $$^{187}$$Os are evaluated from the photodisintegration data with the Hauser-Feshbach statistical model. We quantitatively discuss the two corrections factors for the s-process branchings and the neutron capture on the 9.75 keV state.

Journal Articles

$$s$$-process branching at $$^{185}$$W revised

Mohr, P.*; Shizuma, Toshiyuki; Ueda, Hiroyasu*; Goko, Shinji*; Makinaga, Ayano*; Hara, Kaoru*; Hayakawa, Takehito; Lui, Y.-W.*; Ogaki, Hideaki*; Utsunomiya, Hiroaki*

Physical Review C, 69(3), p.032801_1 - 032801_4, 2004/03

 Times Cited Count:33 Percentile:83.72(Physics, Nuclear)

The neutron capture cross section of the unstable s-process branching nucleus $$^{185}$$W has been derived from experimental data of the inverse $$^{186}$$W($$gamma$$,n)$$^{185}$$W photodisintegration taken with monochromatic photon beams from laser Compton scattering. The result of $$sigma = 553 pm 60$$mb at $$kT = 30$$keV leads to a relatively high effective neutron density in the classical s process of $$N_{rm{n}} = 4.7 times 10^8,{rm{cm}}^{-3}$$. A realistic model for the s process in thermally pulsing AGB stars overestimates the abundance of $$^{186}$$Os significantly because of the relatively small neutron capture cross section of $$^{185}$$W.

Journal Articles

Alpha-decay rates of Yb and Gd in solar-neutrino detectors

Fujiwara, Mamoru; Kawabata, Takahiro*; Mohr, P.*

Journal of Physics G; Nuclear and Particle Physics, 28(4), p.643 - 648, 2002/04

 Times Cited Count:13 Percentile:58.71(Physics, Nuclear)

no abstracts in English

Oral presentation

Excited states and $$gamma$$-ray transition probability on $$^{180}$$Ta and its effects to supernova neutrino process and s-process

Hayakawa, Takehito; Chiba, Satoshi; Kajino, Toshitaka*; Mathews, G. J.*; Mohr, P.*

no journal, , 

We have discuss nuclear structure of $$^{180}$$Ta, excited states and $$gamma$$ transition probabilities, and its effects to supernova neutrino nucleosynthesis and slow neutron capture reaction processes. The ground state of $$^{180}$$Ta beta decays with a half-life of about 8 hours, whereas an isomer at 77 keV is meta-stable state. In hot temperature environments in stars, the ground state and the isomer are linked through highly excited states by ($$gamma$$, $$gamma$$') reactions.

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