Academia.eduAcademia.edu

Figure 2 – uploaded by J. Gaardhoje

See full PDFdownloadDownload figure
TABLE II. Energy (Ep) and width (Tp) of GDR extracted at different excitation energies in '10,112Sn. All energies are in MeV.

Table 2 II. Energy (Ep) and width (Tp) of GDR extracted at different excitation energies in '10,112Sn. All energies are in MeV.

Related Figures (10)

FIG. 1. Schematic diagram of the experimental setup. The nultiplicity filter consists of ten 7.6 10.2 cm Nal detectors.
FIG. 1. Schematic diagram of the experimental setup. The nultiplicity filter consists of ten 7.6 10.2 cm Nal detectors.
FIG. 3. Gamma spectrum measured in ''B(p,y) at E,=7 MeV. The dashed spectrum is from an EGS calculation for the two peaks at 17.94 and 22.37 MeV.
FIG. 3. Gamma spectrum measured in ''B(p,y) at E,=7 MeV. The dashed spectrum is from an EGS calculation for the two peaks at 17.94 and 22.37 MeV.
FIG. 4. Ratio spectrum measured in '°O+ Mo at 140 MeV. The arrows define the gate around Ro (normalized to 1.0) used in the data analysis for pileup rejection.
FIG. 4. Ratio spectrum measured in '°O+ Mo at 140 MeV. The arrows define the gate around Ro (normalized to 1.0) used in the data analysis for pileup rejection.
FIG. 5. Fold distribution of y rays measured in the reaction °F 4 3Nb at three energies. Statistical errors are of the size of the data points. The fits shown by the continuous lines are obtained with Gaussian multiplicity distributions with (a) M=16.0, o=5.2 at 160 MeV, (b) M=14.5, o=3.9 at 100 MeV, and (c) M=12.5, g=3.3 at 80 MeV.
FIG. 5. Fold distribution of y rays measured in the reaction °F 4 3Nb at three energies. Statistical errors are of the size of the data points. The fits shown by the continuous lines are obtained with Gaussian multiplicity distributions with (a) M=16.0, o=5.2 at 160 MeV, (b) M=14.5, o=3.9 at 100 MeV, and (c) M=12.5, g=3.3 at 80 MeV.
TABLE I. Experimental y multiplicities M, computed statistical multiplicities Ms and extracted average E11 yrast multiplicities M, at various bombarding energies in °F + Nb. Jy, and Jaz are cal- culated average angular momenta in compound and residue nuclei, respectively. The y decay rate from (£,,J;) to a final state (Ey,J,) can be similarly written as The hydrodynamical model predicts the isovector gi- ant quadrupole resonance (IVGQR) at an _ energy Egqg=1.6 Egp. The strength function for this mode can be included in statistical model calculation in com- plete analogy to that of the E1 mode. The expression for the strength function Fp [Eq. (7)] was derived'® using a Lorentzian shape for the E1 photoabsorption cross section on the excited final state. On the assumption of a Lorentzian photoabsorption cross section also for the IVGQR and using the Gellman-Telegdi sum rule rela- tion for this mode, i.e.,
TABLE I. Experimental y multiplicities M, computed statistical multiplicities Ms and extracted average E11 yrast multiplicities M, at various bombarding energies in °F + Nb. Jy, and Jaz are cal- culated average angular momenta in compound and residue nuclei, respectively. The y decay rate from (£,,J;) to a final state (Ey,J,) can be similarly written as The hydrodynamical model predicts the isovector gi- ant quadrupole resonance (IVGQR) at an _ energy Egqg=1.6 Egp. The strength function for this mode can be included in statistical model calculation in com- plete analogy to that of the E1 mode. The expression for the strength function Fp [Eq. (7)] was derived'® using a Lorentzian shape for the E1 photoabsorption cross section on the excited final state. On the assumption of a Lorentzian photoabsorption cross section also for the IVGQR and using the Gellman-Telegdi sum rule rela- tion for this mode, i.e.,
FIG. 6. Experimental data and CASCADE fits in (a) SF 4%3Nb at Eveam =80 MeV, (b) °F + °Nb at Eveam = 100 MeV, (c) '*O + *Mo at Epeam = 140 MeV, and (d) °F + *Nb at Eveam = 160 MeV. The solid curves are obtained with only the GDR strength function using the level density parameter a=A/9. The dashed curves at higher energies include also the IVGQR strength function. The fit parameters are listed in Table II (see text). We now discuss the results on the energies and widths of the GDR. The values obtained in the present work, and the widths reported recently by Gaardhoje et al.? for the same mass region are plotted in Fig. 8 as a func-
FIG. 6. Experimental data and CASCADE fits in (a) SF 4%3Nb at Eveam =80 MeV, (b) °F + °Nb at Eveam = 100 MeV, (c) '*O + *Mo at Epeam = 140 MeV, and (d) °F + *Nb at Eveam = 160 MeV. The solid curves are obtained with only the GDR strength function using the level density parameter a=A/9. The dashed curves at higher energies include also the IVGQR strength function. The fit parameters are listed in Table II (see text). We now discuss the results on the energies and widths of the GDR. The values obtained in the present work, and the widths reported recently by Gaardhoje et al.? for the same mass region are plotted in Fig. 8 as a func-
FIG. 9. Comparison of the energies of the ground state GDR’s for mass A =115-124 and of the excited state GDR for A =110—-112. Two available sets for ground state data (Refs. 23 and 24) are plotted. The dashed line extrapolates the ground state values to the mass region A~111. The excited state value is the average for four excitation energies obtained in this work. FIG. 8. Energy (a) and width (b) of the GDR extracted from the present data at different excitation energies in the compound nuclei ''°''§n. The widths obtained in an earlier work (Ref. 9) are shown by open circles. The ground state GDR width obtained from (y,) work is also indicated. The curve through the data points in (b) is described by Eq. (15) of the text. FIG. 7. The “divided plots” of the experimental data and the CASCADE fits shown in Fig. 6, at various bombarding energies The ordinate is proportional to the strength function G(E,)=F(E,)/E ; (F(E,) is defined in the text). The solid curves show the single Lorentzian fits on a linear scale. The dashed curve in (d) at 160 MeV is obtained by adding to the main Lorentzian com. ponent (Ep = 14.6 MeV, ['p =10.5 MeV), another component (Ep =8.8 MeV, Ip =3.0 MeV) having 5% strength.
FIG. 9. Comparison of the energies of the ground state GDR’s for mass A =115-124 and of the excited state GDR for A =110—-112. Two available sets for ground state data (Refs. 23 and 24) are plotted. The dashed line extrapolates the ground state values to the mass region A~111. The excited state value is the average for four excitation energies obtained in this work. FIG. 8. Energy (a) and width (b) of the GDR extracted from the present data at different excitation energies in the compound nuclei ''°''§n. The widths obtained in an earlier work (Ref. 9) are shown by open circles. The ground state GDR width obtained from (y,) work is also indicated. The curve through the data points in (b) is described by Eq. (15) of the text. FIG. 7. The “divided plots” of the experimental data and the CASCADE fits shown in Fig. 6, at various bombarding energies The ordinate is proportional to the strength function G(E,)=F(E,)/E ; (F(E,) is defined in the text). The solid curves show the single Lorentzian fits on a linear scale. The dashed curve in (d) at 160 MeV is obtained by adding to the main Lorentzian com. ponent (Ep = 14.6 MeV, ['p =10.5 MeV), another component (Ep =8.8 MeV, Ip =3.0 MeV) having 5% strength.
Related topics:
PhysicsMedicine
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved