Search results for "Excitation"
showing 10 items of 1290 documents
Evolution from γ -soft to stable triaxiality in Nd136 as a prerequisite of chirality
2018
The level structure of Nd136 has been investigated using the Mo100(Ar40,4n) reaction and the JUROGAM II+RITU+GREAT setup. The level scheme has been extended significantly. Many new bands have been identified both at low and high spin, among which are five nearly degenerate bands interpreted as chiral partners. Excitation energies, spins, and parities of the previously known bands are revised and firmly established, and some previously known bands have been revised. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. The band structure of Nd136 is now clarified and the various types of single-particle and collective excitations are well underst…
Detailed spectroscopy of Bi195
2017
An experiment focused on the study of shape coexistence and new high-spin structures in $^{195}\mathrm{Bi}$ has been performed. The nucleus is in a transitional region of the bismuth isotope chain. A large number of new states have been found, resulting in a significant extension of the previously known level scheme. Several new collective structures have been identified. A strongly coupled rotational band built upon the $13/{2}^{+}$ isomeric state was extended up to ${I}^{\ensuremath{\pi}}=(49/{2}^{+})$ and an energy of 5706 keV. The ${I}^{\ensuremath{\pi}}=31/{2}^{+}$ member of the $\ensuremath{\pi}{i}_{13/2}$ band was also found to feed a new long-lived isomeric state with an excitation …
Single-Particle Excitations and Collective Vibrational Modes in 96Zr
1988
New results from (n,n’γ) and (p,p’γ) reactions, as well as from β- decay confirm the double subshell closure in 96Zr and provide a detailed level scheme for this nucleus. The 1750 keV first 2+ state is described as a neutron particle-hole excitation, while the positive-parity band built on the 1582 keV excited 0+ state is characterised by quadrupole vibrational collectivity at low spins. Candidates for two-phonon octupole, quadrupole-octupole and higher multipole states are suggested on the basis of fast El and E2 decays to the 3- octupole state. The recently observed large octupole strength, its inverse relationship with the filling of the νlh11/2 orbital, and the onset of quadrupole defor…
Excitation of singlet–triplet coherences in pairs of nearly-equivalent spins
2019
We present approaches for an efficient excitation of singlet–triplet coherences in pairs of nearly-equivalent spins. Standard Nuclear Magnetic Resonance (NMR) pulse sequences do not excite these coherences at all or with very low efficiency. The single quantum singlet–triplet coherences, here termed the outer singlet–triplet coherences, correspond to lines of low intensity in the NMR spectrum of a strongly-coupled spin pair (they are sometimes referred to as “forbidden transitions”), whereas the zero-quantum coherences, here termed the inner singlet–triplet coherences, do not have a direct spectral manifestation. In the present study, we investigated singlet–triplet coherences in a pair of …
Absolute frequency measurements on the 2S→3S transition of lithium-6,7
2009
The frequencies of the 2S–3S two-photon transition for the stable lithium isotopes were measured by cavity-enhanced Doppler-free laser excitation that was controlled by a femtosecond frequency comb. The resulting values of 815 618 181.57(18) and 815 606 727.59(18) MHz, respectively, for 7Li and 6Li are in agreement with previous measurements but are more accurate by an order of magnitude. There is still a discrepancy of about 11.6 and 10.6 MHz from the latest theoretical values. This is comparable to the uncertainty in the theoretical calculations, while uncertainty in our experimental values is more than a hundred-fold smaller. More accurate theoretical calculation of the transition freque…
Evolution of collectivity in the78Ni region: Coulomb excitation of74Ni at intermediate energies.
2014
The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic ob- servables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the ef- fective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope ( 64 Ni) towards the 78 Ni nucleus where the large neu…
The photospheric abundances of active binaries II. Atmospheric parameters and abundance patterns for 6 single-lined RS CVn systems
2003
Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been derived for 13 chemical species, including several key elements such as Li, Mg, and Ca. Two methods have been used. The effective temperatures, surface gravities and microturbulent velocities were first derived from a fully self-consistent analysis of the spectra, whereby the temperature is determined from the excitation equilibrium of the Fe I lines. The second approach relies on temperatures derived from the (B-V) colour index. These two methods give broadly consistent results for the stars in …
Phänomenologische Betrachtung zur Photon-Elektron-Wechselwirkung in einem Plasma
1961
The question at stake is, whether a simple physical connection may be found between Richardson equation for thermionic emission on the one hand, and Richardson equation for photoelectric emission on the other hand. The proposition of such a connection is based on the following supposition: that electrons are not only elements of a (Fermi-Dirac-) statistical ensemble and, as such, cause thermionic phenomena; but that they can also interact with a radiation field, thereby causing an additional emission current, according to Richardson (photoelectric) equation. — It is shown in detail that the current emitted from a metal of 2000 °K is determined by the complete radiation of this metal only to…
Steady-state emission and stability of a single-mode two-level Fabry-Perot cavity laser
1997
Abstract An analytical steady-state solution for a single-mode homogeneously-broadened two-level Fabry-Perot laser, valid for any field intensity, cavity detuning and level-population decay rates, is obtained. A power-series expansion of this solution allows to perform a linear stability analysis which reveals the existence of two Hopf bifurcations instead of one as in unidirectional ring lasers. These bifurcations delimit the domain of unstable emission of the laser with respect to small perturbations. The instability threshold for hard-mode excitation is higher than in a ring laser, although introduction of a small definite detuning makes them similar. The time-dependent behaviour above t…
Rotational features of vibrator nucleus118Te
1999
High-spin states in ${}^{118}\mathrm{Te}$ have been populated via heavy-ion induced reactions. Excited states were observed up to $I=32\ensuremath{\Elzxh}$ and, in addition to irregular level sequences, several bands were identified for the first time. The decoupled negative parity bands based upon ${7}^{\ensuremath{-}}$ and ${8}^{\ensuremath{-}}$ states are interpreted to arise from the proton ${h}_{11/2}{g}_{7/2}$ configuration coupled to the $2p\ensuremath{-}2h$ intruder states in ${}^{116}\mathrm{Sn}.$ These bands show very smooth alignment behavior, in accordance with the proton ${h}_{11/2}$ bands in neighboring Sb and I nuclei. Above $I=20$ the yrast positive parity band is built on t…