Lifetime measurements in
178
Pt with excited states de-exciting through
γ
-ray transitions and internal electron conversions have been performed. Ionic charges were selected by the in-flight mass ...separator MARA and measured at the focal plane in coincidence with the
4
1
+
→
2
1
+
257
keV
γ
-ray transition detected using the JUROGAM 3 spectrometer. The resulting charge-state distributions were analysed using the differential decay curve method (DDCM) framework to obtain a lifetime value of 430(20) ps for the
2
1
+
state. This work builds on a method that combines the charge plunger technique with the DDCM analysis. As an alternative analysis, ions were selected in coincidence with the
178
Pt alpha decay (
E
alpha
=
5.458
(
5
)
MeV) at the focal plane. Lifetime information was obtained by fitting a two-state Bateman equation to the decay curve with the lifetime of individual states defined by a single quadrupole moment. This yielded a lifetime value of 430(50) ps for the
2
1
+
state, and 54(6) ps for the
4
1
+
state. An analysis method based around the Bateman equation will become especially important when using the charge plunger method for the cases where utilising coincidences between prompt
γ
rays and recoils is not feasible.
We prepared {11−22} GaN layers with different thicknesses on r‐plane patterned sapphire substrates (r‐PSS) through metal‐organic vapor phase epitaxy. In order to obtain a {11−22} GaN layer of high ...crystalline quality, a wide terrace was adopted for the r‐PSS according to the expansion of the laterally overgrown region. Using scanning electron microscopy and cathodoluminescence (CL) imaging, we observed that the defects are arranged along lines in certain directions and that their number increases with increasing thickness. These defects are expected to be dislocation clusters by CL measurement at 7 K. For the {11−22} GaN layer with anomalous defects (dark spots), the defects are arranged along a line tilted from the c‐axis of the GaN layer through a glide of the m‐plane in semipolar GaN, which is considered to be generated by the relaxation of the strained GaN layer.
High-spin states of the odd–odd
194
Bi nucleus have been studied by means of nuclear spectroscopy for the first time. Two low-lying rotational bands were observed. The positive-parity band built on a ...short-lived isomeric state 633 keV above the
α
and
β
decaying long-lived (10
-
) state is assigned a
π
i
13
/
2
⊗
ν
i
13
/
2
-
1
configuration, while the other band is attributed to the
π
h
9
/
2
⊗
ν
i
13
/
2
-
1
configuration. Both of these bands are assumed to have oblate shape. Three band-like structures composed predominantly of
Δ
I
=
1
transitions were also found. One of the shears band candidates is firmly linked to the lower lying level structures whereas for the other two links to lower-lying structures remain missing.
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
≥
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
≥
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.
The physics program at the super-conducting fragment separator (Super-FRS) at FAIR, being operated in a multiple-stage, high-resolution spectrometer mode, is discussed. The Super-FRS will produce, ...separate and transport radioactive beams at high energies up to 1.5 AGeV, and it can be also used as a stand-alone experimental device together with ancillary detectors. Various combinations of the magnetic sections of the Super-FRS can be operated in dispersive, achromatic or dispersion-matched spectrometer ion-optical modes, which allow measurements of momentum distributions of secondary-reaction products with high resolution and precision. A number of unique experiments in atomic, nuclear and hadron physics are suggested with the Super-FRS as a stand-alone device, in particular searches for new isotopes, studies of hypernuclei, delta-resonances in exotic nuclei and spectroscopy of atoms characterized by bound mesons. Rare decay modes like multiple-proton or neutron emission and the nuclear tensor force observed in high-momentum regime can be also addressed. The in-flight radioactivity measurements as well as fusion, transfer and deep-inelastic reaction mechanisms with the slowed-down and energy-bunched fragment beams are proposed for the high-resolution and energy buncher modes at the Super-FRS.
Excited states have been identified in the heaviest known even-ZN=84 isotone 158W, which lies in a region of one-proton emitters and the two-proton drip line. The observation of γ-ray transitions ...feeding the ground state establishes the excitation energy of the yrast 6+ state confirming the spin-gap nature of the α-decaying 8+ isomer. The 8+ isomer is also expected to be unbound to two-proton emission but no evidence for this decay mode was observed. An upper limit for the two-proton decay branch has been deduced as b2p≤ 0.17% at the 90% confidence level. The possibility of observing two-proton emission from multiparticle isomers in nearby nuclides is considered.
The far-field distribution of the emission intensity of terahertz (THz) quantum-cascade lasers (QCLs) frequently exhibits multiple lobes instead of a single-lobed Gaussian distribution. We show that ...such multiple lobes can result from self-interference related to the typically large beam divergence of THz QCLs and the presence of an inevitable cryogenic operation environment including optical windows. We develop a quantitative model to reproduce the multiple lobes. We also demonstrate how a single-lobed far-field distribution can be achieved.
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