The production of the
180
m
Hf
nuclei in the photoproton reaction
181
Ta
(
γ
,
p
)
was studied at end-point bremsstrahlung energies
E
γ
max
=
35
–95 MeV. The experiment was performed at the electron ...linear accelerator LUE-40 NSC KIPT with the use of the
γ
activation and off-line
γ
-ray spectroscopy. The experimental values of the bremsstrahlung flux-averaged cross-sections
⟨
σ
(
E
γ
max
)
⟩
m
for the
181
Ta
(
γ
,
p
)
180
m
Hf
reaction were determined, and at
E
γ
max
>
55
MeV obtained for the first time. The measured values, as well as the literature data, significantly (by more that an order of magnitude) exceed the theoretical flux-averaged cross-sections
⟨
σ
(
E
γ
max
)
⟩
th
. The
⟨
σ
(
E
γ
max
)
⟩
th
values were calculated using the cross-section
σ
(
E
)
computed with the TALYS1.95 code for six different level density models. A comparative analysis of the calculated total cross-sections from the TALYS computation for the reactions
181
Ta
(
γ
,
p
)
180
Hf
and
181
Ta
(
γ
,
n
)
180
Ta
was performed. It was shown that the photoproton
(
γ
,
p
)
to photoneutron
(
γ
,
n
)
strength ratio is consistent with the estimates based on the isospin selection rules and the value from the
(
e
,
e
′
p
)
experiment.
Abstract
The production of the
$$^{180\textrm{m}}\textrm{Hf}$$
180
m
Hf
nuclei in the photoproton reaction
$${^{181}\textrm{Ta}}(\gamma ,p)$$
181
Ta
(
γ
,
p
)
was studied at end-point bremsstrahlung ...energies
$$E_{\mathrm{\gamma max}}=35$$
E
γ
max
=
35
–95 MeV. The experiment was performed at the electron linear accelerator LUE-40 NSC KIPT with the use of the
$$\gamma $$
γ
activation and off-line
$$\gamma $$
γ
-ray spectroscopy. The experimental values of the bremsstrahlung flux-averaged cross-sections
$$\langle {\sigma (E_{\mathrm{\gamma max}})}\rangle _{\textrm{m}}$$
⟨
σ
(
E
γ
max
)
⟩
m
for the
$${^{181}\textrm{Ta}}(\gamma ,p)^{180\textrm{m}}\textrm{Hf}$$
181
Ta
(
γ
,
p
)
180
m
Hf
reaction were determined, and at
$$E_{\mathrm{\gamma max}} > 55$$
E
γ
max
>
55
MeV obtained for the first time. The measured values, as well as the literature data, significantly (by more that an order of magnitude) exceed the theoretical flux-averaged cross-sections
$$\langle {\sigma (E_{\mathrm{\gamma max}})}\rangle _{\textrm{th}}$$
⟨
σ
(
E
γ
max
)
⟩
th
. The
$$\langle {\sigma (E_{\mathrm{\gamma max}})}\rangle _{\textrm{th}}$$
⟨
σ
(
E
γ
max
)
⟩
th
values were calculated using the cross-section
$$\sigma (E)$$
σ
(
E
)
computed with the TALYS1.95 code for six different level density models. A comparative analysis of the calculated total cross-sections from the TALYS computation for the reactions
$${^{181}\textrm{Ta}}(\gamma ,p)^{180}\textrm{Hf}$$
181
Ta
(
γ
,
p
)
180
Hf
and
$${^{181}\textrm{Ta}}(\gamma ,n)^{180}\textrm{Ta}$$
181
Ta
(
γ
,
n
)
180
Ta
was performed. It was shown that the photoproton
$$(\gamma ,p)$$
(
γ
,
p
)
to photoneutron
$$(\gamma ,n)$$
(
γ
,
n
)
strength ratio is consistent with the estimates based on the isospin selection rules and the value from the
$$(e,e'p)$$
(
e
,
e
′
p
)
experiment.
A new automated method has been developed with the aim to correct measured spectra for sudden gain and offset drifts due to temporal instrumentation instabilities. It is based on discrete ...cross-correlation that alleviates the need for Gaussian-shaped peaks and is capable of correcting spectra that change their shape in time. Potential of this method has been tested on decay and in-beam γ-ray spectroscopy data measured with an array of three n-type coaxial High-Purity Germanium detectors albeit its use is not limited only for γ-ray spectroscopy.
This letter reports lifetime measurements of excited states in the odd-N nucleus 163W using the recoil-distance Doppler shift method to probe the core polarising effect of the i13/2 neutron orbital ...on the underlying soft triaxial even-even core. The ratio B(E2:21/2+→17/2+)/B(E2:17/2+→13/2+) is consistent with the predictions of the collective rotational model. The deduced B(E2) values provide insights into the validity of collective model predictions for heavy transitional nuclei and a geometric origin for the anomalous B(E2) ratios observed in nearby even-even nuclei is proposed.
Decay spectroscopy of the odd-proton nuclei $^{249}$Md and $^{251}$Md has been performed. High-K isomeric states were identified for the first time in these two nuclei through the measurement of ...their electromagnetic decay. An isomeric state with a half-life of 2.8(5) ms and an excitation energy $\ge 910$ keV was found in $^{249}$Md. In $^{251}$Md, an isomeric state with a half-life of 1.4(3) s and an excitation energy $\ge 844$ keV was found. Similarly to the neighbouring $^{255}$Lr, these two isomeric states are interpreted as 3 quasi-particle high-K states and compared to new theoretical calculations. Excited nuclear configurations were calculated within two scenarios: via blocking nuclear states located in proximity to the Fermi surface or/and using the quasiparticle Bardeen–Cooper–Schrieffer method. Relevant states were selected on the basis of the microscopic-macroscopic model with a deformed Woods–Saxon potential. The most probable candidates for the configurations of K-isomeric states in Md nuclei are proposed.
Low-lying states in the odd-Z isotopes Ac13289221 and Pa13491225 have been studied using α-particle and αγ-coincidence spectroscopy in the Pa225→Ac221→Fr217 decay chain. Ground-state spin and parity ...assignments of Iπ = 5/2- are proposed for both Ac221 and Pa225, with the odd proton occupying the ω = 5/2 orbital of the quadrupole-octupole deformed shell model in both nuclei. In Ac221, excited states in the bands based on the ω = 5/2 and ω = 3/2 orbitals have been identified, including proposed parity-doublet states. The results suggest that reflection-asymmetric deformation of the ground state persists in the odd-A members of the isotope chains down to N = 132 for Ac and N = 134 for Pa, before reaching the transitional region at N = 130.
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