Photodisintegration of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Be</mml:mi></mml:mrow><mml:mrow><mml:mn>9</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>from Threshold to 5 Mev

Jakobson, M. J.

doi:10.1103/physrev.123.229

Cited by 69 publications

(23 citation statements)

References 8 publications

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“…Previous 9 Be photodisintegration studies are numerous [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] but reveal relatively large cross-section uncertainties in the astrophysically important region near the neutron emission threshold. New (γ, n) cross-section measurements with improved accuracy are now possible using intense photon beams with small energy spreads and neutron detectors with large solid angle coverage and high efficiencies.…”

Section: Introductionmentioning

confidence: 99%

Cross-section measurement of9Be(γ,n)8Be and implications for
Arnold
¹
,
Clegg
²
,
Iliadis
³

et al. 2012
Phys. Rev. C

146

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Models of the r process are sensitive to the production rate of 9 Be because, in explosive environments rich in neutrons, α(αn, γ ) 9 Be is the primary mechanism for bridging the stability gaps at A = 5 and A = 8. The α(αn, γ ) 9 Be reaction represents a two-step process, consisting of α + α → 8 Be followed by 8 Be(n, γ ) 9 Be. We report here on a new absolute cross-section measurement for the 9 Be(γ, n) 8 Be reaction conducted using a highly efficient, 3 He-based neutron detector and nearly monoenergetic photon beams, covering energies from E γ = 1.5 MeV to E γ = 5.2 MeV, produced by the High Intensity γ -ray Source of Triangle Universities Nuclear Laboratory. In the astrophysically important threshold energy region, the present cross sections are 40% larger than those found in most previous measurements and are accurate to ±10% (95% confidence). The revised thermonuclear α(αn, γ ) 9 Be reaction rate could have implications for the r process in explosive environments such as type II supernovae.

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Section: Introductionmentioning

confidence: 99%

Cross-section measurement of9Be(γ,n)8Be and implications for
Arnold
¹
,
Clegg
²
,
Iliadis
³

et al. 2012
Phys. Rev. C

146

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“…Early measurements of photoneutron cross sections for 9 Be were carried out with monochromatic γ rays from radioactive isotopes [22,23,24,25,26] and with bremsstrahlung [27,28].…”

Section: Resonances Of 9 Bementioning

confidence: 99%

Astrophysical reaction rate for α(αn,γ)9Be by photodisintegration

et al. 2002

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We study the astrophysical reaction rate for the formation of 9 Be through the three body reaction α(αn, γ). This reaction is one of the key reactions which could bridge the mass gap at A = 8 nuclear systems to produce intermediate-to-heavy mass elements in alpha-and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable 8 Be, α + α ⇀ ↽ 8 Be(n,γ) 9 Be. Off-resonant and on-resonant contributions from the ground state in 8 Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of 9 Be with laser-electron photon beams, which covers all relevant resonances in 9 Be. Experimental data near the neutron threshold are added with γ-ray flux corrections and a new least-squares analysis is made to deduce resonance parameters in the Breit-Wigner formulation. Based on the photodisintegration cross section, we provide the reaction rate for α(αn, γ) 9 Be in the temperature range from T 9 =10 −3 to T 9 =10 1 (T 9 is the temperature in units of 10 9 K) both in the tabular form and in the analytical form for potential usage in nuclear reaction network calculations.The calculated reaction rate is compared with the reaction rates of the CF88 and the NACRE compilations. The CF88 rate, which is based on the photoneutron cross section for the 1/2 + state in 9 Be by Berman et al., is valid at T 9 > 0.028 due to lack of the off-resonant contribution. The CF88 rate differs from the present rate by a factor of two in a temperature range T 9 ≥ 0.1. The NACRE rate, which adopted different sources of experimental information on resonance states in 9 Be, is 4-12 times larger than the present rate at T 9 ≤ 0.028, but is consistent with the present rate to within ±20% at T 9 ≥ 0.1. 2

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“…The errors indicated are the standard deviations of the mean values for 20 measurements (hereafter errors shown are the standard deviations of the mean values, unless otherwise noted). From these results the net counting rates of neutrons are obtained as C,, = 159 + 4 per 30 rnin Ccl = 1597 +_ 9 per 5 rnin Although a y ray of energy 3810 keV is emitted from 38CI, its intensity relative to the 2168 keV y ray has been measured to be 6.1 x lop4 (5), while the cross section ~(3810) is nearly equal to ~(2168) (6). Therefore the effects of this y ray on the counting rate C,, can be neglected.…”

Section: Counting Rates C and Co Of Neutronsmentioning

confidence: 99%

Measurement of the crossover E4 transition (2009.8 keV) in ⁴⁶Ti

Fujishiro¹,

Satoh²,

Okamoto³

et al. 1980

Can. J. Phys.

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The photonuclear reaction 9Be(y,n) was used to measure the intensity I(2009.8) of the crossover E4 transition in 46Ti by an improved method. A point-like 4 6 S~ source was used to provide the 4hTi. Neutrons generated by the "Ti gamma rays were detected with BF, counters. The observedintensity perdecay o~~~S C was1(2009.8)= (1.3 + 1.0) x lo-', whichagrees well with the previous estimate by Fluharty and Deutsch. From the present result the reduced transition probability B(E4),, and the partial mean life-time r(E4) of the crossover E4 transition between the 2009.8 keV, 4+ state and the ground state in 46Ti were estimated as B(E4),,= (5.6 + 4.9) x e2 cms and r(E4) = (1.7 + 1.3) x s, respectively. On a utilise la reaction photonucleaire 9Be(y,n) pour mesurer I'intensite I(2009.8) de la transition de croisement E4 dans 46Ti par une methode amelioree. Une source ponctuelle de 4 6 S~ a ete employee pour fournir le 46Ti. Les neutrons produits par les rayons gamma de 46Ti etaient detectes par des compteurs BF,. L'intensite observee par desintegration de 4bSc est 1(2009,8) = (I, 3 + 1.0) x 10-',ce quiest en bon accordavec I'estimation anterieurede Fluharty et Deutsch. A partir du present resultat la probabilite reduite de transition B(E4),, et la vie moyenne partielle 7(E4) de la transition de croisement E4 entre l'etat 2009.8 keV, 4+, et I'etat fondamental de 46Ti ont ete estimees a B(E4),, = (5,6 + 4.9) x e' cm8 et r(E4) = (1.7 If: 1,3) x s, respectivement. Can. J. Phys.,58. 1712(1980) [Traduit par le journal] 4 ' The crossover E4 transitions from low-lying 4+ 83.9 dexcited states in spherical even-even nuclei are of 2 , , + / 4+ -? interest especially in connection with the collective behavior of nuclear matter. However, previous 100 % 6.2 experimental data were not good enough to compare with theory. In addition to the extreme weak-3 Q? l ness of the E4 transition the presence of the sum peak due to cascade E2 transitions makes it very 889.3 difficult, even with a Ge(Li) detector, to measure its I intensity accurately. A comparatively simple method is to use the photonuclear (y,n) reaction o 4 6and to count the neutrons generated. However, this Ti method requires an intense y-ray source (a fewtens of curies at least). which is accom~anied bv FIG. 1. Partial decay scheme of 4 6 S~ (all energies in keV).troublesome proble'hs in its production: handling, the 0+ ground state, the former being populated and disposal. Hence the method has been applied through the allowed P-decay of 4 6 S~ with an intenmainly to the measurement of the crossover E4 sity of 100%. transition (2506 keV) in 60Ni using a familiar 60Co source for the D(y ,n) reaction (1-3). MethodThe photonuclear reaction 9Be(y ,n) is used here Figure 2 shows the experimental arrangement for to measure the intensity of the crossover E4 transi-the present measurements. A 4 6 S~ source of about tion in 46Ti, and some nuclear information is extra-23 Ci is placed at the center of the cylindrical target cted from the results obtained. Figure 1 shows the assembly which con...

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Photodisintegration ofBe9from Threshold to 5 Mev

Cited by 69 publications

References 8 publications

Cross-section measurement of9Be(γ,n)8Be and implications for
Arnold
¹
,
Clegg
²
,
Iliadis
³

et al. 2012
Phys. Rev. C

Cross-section measurement of9Be(γ,n)8Be and implications for
Arnold
¹
,
Clegg
²
,
Iliadis
³

et al. 2012
Phys. Rev. C

Astrophysical reaction rate for α(αn,γ)9Be by photodisintegration

Measurement of the crossover E4 transition (2009.8 keV) in ⁴⁶Ti

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Photodisintegration ofBe9from Threshold to 5 Mev

Cited by 69 publications

References 8 publications

Cross-section measurement of9Be(γ,n)8Be and implications forArnold1, Clegg2, Iliadis3 et al. 2012Phys. Rev. C

Cross-section measurement of9Be(γ,n)8Be and implications forArnold1, Clegg2, Iliadis3 et al. 2012Phys. Rev. C

Astrophysical reaction rate for α(αn,γ)9Be by photodisintegration

Measurement of the crossover E4 transition (2009.8 keV) in 46Ti

Contact Info

Product

Resources

About

Cross-section measurement of9Be(γ,n)8Be and implications for
Arnold
¹
,
Clegg
²
,
Iliadis
³

et al. 2012
Phys. Rev. C

Cross-section measurement of9Be(γ,n)8Be and implications for
Arnold
¹
,
Clegg
²
,
Iliadis
³

et al. 2012
Phys. Rev. C

Measurement of the crossover E4 transition (2009.8 keV) in ⁴⁶Ti