Study Of Parity Nonconservation Research Articles

Radiative transition properties including line strengths, oscillator strengths, and transition rates for Ra II

In this paper, we calculate the energy and radiative transition properties of singly charged Ra using the singles and doubles approximated relativistic coupled-cluster method. The excitation energies of the (7 - 12)S1/2, (7 - 12)P1/2,3/2, (6 - 10)D3/2,5/2 states in Ra+ are reported. The results are compared with available experimental results, showing a good agreement. Accurate values along with their uncertainties of the electric-dipole (E1), electric-quadrupole (E2), and several important magnetic-dipole (M1) matrix elements for transitions in singly charged Ra are determined by the relativistic coupled-cluster method at different approximations. Using these computed E1, E2, and M1 matrix elements, we also provide the related radiative transition properties of Ra+, including line strengths, oscillator strengths, and transition rates. Furthermore, we also investigate the role of electron correlation in these properties. To the best of our knowledge, many results are reported for the first time. Present work reports a high-precision atomic property calculation of Ra+ and is beneficial for present and future experiments using Ra+ targeting various applications such as atomic clocks and studies of parity non-conservation.

Hyperfine Anomalies in Fr: Boundaries of the Spherical Single Particle Model

We have measured the hyperfine splitting of the 7P_{1/2} state at the 100 ppm level in Fr isotopes (^{206g,206m,207,209,213,221}Fr) near the closed neutron shell (N=126 in ^{213}Fr). The measurements in five isotopes and a nuclear isomeric state of francium, combined with previous determinations of the 7S_{1/2} splittings, reveal the spatial distribution of the nuclear magnetization, i.e., the Bohr-Weisskopf effect. We compare our results with a simple shell model consisting of unpaired single valence nucleons orbiting a spherical nucleus, and find good agreement over a range of neutron-deficient isotopes (^{207-213}Fr). Also, we find near-constant proton anomalies for several even-N isotopes. This identifies a set of Fr isotopes whose nuclear structure can be understood well enough for the extraction of weak interaction parameters from parity nonconservation studies.

Compton polarimetry using double-sided segmented x-ray detectors

Hard x-ray polarimetry of radiation emitted in collisions of heavy ions, electrons or photons with matter provides detailed information on the collision dynamics as well as of the atomic structure in the presence of extreme field strengths. Moreover, it also opens a route for polarization diagnosis of spin-polarized ion and electron beams which, for example, might be useful in future parity non-conservation studies. Owing to recent progress in the development of highly segmented solid-state detectors, a novel type of polarimeter for the hard x-ray regime has become available. Applied as Compton polarimeters, two-dimensional position-sensitive x-ray detectors now allow for precise and efficient measurements of x-ray linear polarization properties. In this report recent polarimetry studies using such detector systems are reviewed.

The FrPNC Experiment, weak interaction studies in Francium at TRIUMF

Francium is an excellent system to study the nuclear weak force due to its large nucleus and relatively simple atomic structure. The FrPNC experiment has a facility to produce cold trapped atomic francium samples for parity non-conservation studies. We are preparing to measure both the nuclear spin independent and dependent parts of the weak interaction in francium. The first one gives information about weak neutral currents at low energies, while the second one is sensitive to weak interactions between nucleons. We present the current status of the experiment.

Hyperfine transitions in He-like ions as a tool for nuclear-spin-dependent parity-nonconservation studies

In this paper a scheme is proposed for measuring nuclear-spin-dependent parity-nonconservation effects in highly charged ions. The idea is to employ circularly polarized laser light for inducing the transition between the level $(1s2s){}^{1}{S}_{0}$ and the hyperfine sublevels of $(1s2s){}^{3}{S}_{1}$ in He-like ions with nonzero nuclear spin. We argue that an interference between the allowed magnetic dipole $M1$ and the parity-violating electric dipole $E1$ decay channel leads to an observable asymmetry of order ${10}^{\ensuremath{-}7}$ in the transition cross section, in the atomic range $28\ensuremath{\leqslant}Z\ensuremath{\leqslant}35$. Experimental requirements for asymmetry measurements are discussed in the case of He-like ${}_{34}^{77}$Se.

Improved RCI techniques for atomic 4f excitation energies: application to Sm I 4f6s2 5DJ levels

We complete the development of a relativistic energy-dependent efficient method by which important pair-correlation effects associated with open subshells can be incorporated into the relativistic configuration interaction (RCI) methodology. We apply this to predict the positions of the 4f6s2 5DJ levels of Sm I. Relative to 5D1, we predict 5D0 lies at −1613 cm−1 and 5D4 at 6589 cm−1. For 5D2 and 5D3, we are 22 cm−1 and 123 cm−1 below the observed difference, respectively. We also calculate magnetic dipole transition rates among these levels and the ground-state 7FJ levels, which may be of interest to future parity nonconservation studies.

Application of relativistic coupled-cluster theory to atomic parity non-conservation

Despite the remarkable success of the standard model, it is widely believed that it is just an intermediate step in understanding the properties of the elementary particles in nature and the interactions between them. Studies of parity non-conservation in atomic systems based on non-accelerator methods have advanced over the years and they have now attained the maturity to test the standard model. The most accurate data from this approach comes from the 6s 2S 1/2→7s 2S 1/2 transition in cesium. An experiment on singly ionized barium has been proposed to carry out a further test of this kind independent of cesium. We discuss here the result of our ab initio calculation of the 6s 2S 1/2→5d 2D 3/2 parity non-conserving electric dipole transition amplitude in 137Ba + based on a novel relativistic coupled-cluster theory. We also discuss a possible improvement of the existing cesium parity non-conservation calculations.

Experimental and theoretical study of the3dD2–level lifetimes ofCa+40

We report measurements of the lifetimes of the $3d\phantom{\rule{0.3em}{0ex}}^{2}D_{5∕2}$ and $3d\phantom{\rule{0.3em}{0ex}}^{2}D_{3∕2}$ metastable states of a single laser-cooled $^{40}\mathrm{Ca}^{+}$ ion in a linear Paul trap. We introduce a measurement technique based on high-efficiency quantum state detection after coherent excitation to the ${D}_{5∕2}$ state or incoherent shelving in the ${D}_{3∕2}$ state, and subsequent free, unperturbed spontaneous decay. The result for the natural lifetime of the ${D}_{5∕2}$ state of 1168(9) ms agrees excellently with the most precise published value. The lifetime of the ${D}_{3∕2}$ state is measured with a single ion and yields 1176(11) ms which improves the statistical uncertainty of previous results by a factor of four. We compare these experimental lifetimes to high-precision ab initio all order calculations [${D}_{3∕2}$ state: 1196(11) ms; ${D}_{5∕2}$ state: 1165(11) ms] and find a very good agreement. These calculations represent an excellent test of high-precision atomic theory and will serve as a benchmark for the study of parity nonconservation in ${\mathrm{Ba}}^{+}$ which has similar atomic structure.

Electric dipole and quadrupole transition amplitudes forBa+using the relativistic coupled-cluster method

We present our calculations of the electric dipole and quadrupole matrix elements for transitions between low-lying bound states of ${\mathrm{Ba}}^{+}$ that are relevant for parity nonconservation studies using the relativistic coupled-cluster method. The results compare well with the experimental data. We have also computed the electric dipole transition matrix elements between many high-lying excited states.

Particle-hole level densities in deformed nuclei

A microscopic combinatorial approach is used to calculate the state and level densities with fixed exciton numbers, in some actinide nuclei. The deformed Woods-Saxon shell model was used as a basis from which all possible configurations were generated. The pairing interaction was taken into account by applying the BCS theory to each configuration. Both the spin and parity distributions were obtained, considering the deformation of the nucleus. Relevance of the result to parity nonconservation studies involving epithermal neutrons on ${}^{238}\mathrm{U}$ and ${}^{232}\mathrm{Th}$ is discussed.

Experimental investigation of excited-state lifetimes in atomic ytterbium.

Lifetimes of 21 excited states in atomic Yb were measured using time-resolved fluorescence detection following pulsed laser excitation. The lifetime of the 4${\mathit{f}}^{14}$5d6${\mathit{s}}^{\mathrm{}3}$${\mathit{D}}_{1}$ state, which is of particular importance for a proposed study of parity nonconservation in atoms, was measured to be 380(30) ns. \textcopyright{} 1996 The American Physical Society.

Parity violation in charged particle nuclear reactions.

The potential role of charged particle resonance reactions in the study of parity nonconservation (PNC) in the nucleus is examined in light of recent statistical interpretations of PNC measurements in neutron resonances. Several PNC observables have been calculated using experimental resonance parameters for five s-d shell nuclei. Longitudinal analyzing powers in (p\ensuremath{\rightarrow},${\mathrm{\ensuremath{\alpha}}}_{0}$) reactions show strong dependence on energy, angle, and resonance parameters. Measurements of analyzing powers at the ${10}^{\mathrm{\ensuremath{-}}4}$ level should provide new information on parity vaiolation in the nucleon-nucleus interaction.

11 262 keV1+state inNe20

The excitation energy of the lowest ${1}^{+}$, $T=1$ state in $^{20}\mathrm{Ne}$, which is important for parity nonconservation studies, has been determined in a photon scattering experiment to be 11 262.3 \ifmmode\pm\else\textpm\fi{} 1.9 keV. Values for the $\ensuremath{\gamma}$-ray branching of this level to the ground state and to the first ${2}^{+}$ level in $^{20}\mathrm{Ne}$ are 84 \ifmmode\pm\else\textpm\fi{} 5% and 16 \ifmmode\pm\else\textpm\fi{} 5%, respectively.NUCLEAR REACTIONS $^{20}\mathrm{Ne}(\ensuremath{\gamma}, \ensuremath{\gamma})$, ${E}_{\ensuremath{\gamma}}<18$ MeV, bremsstrahlung; measured ${E}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}$ branching. Ne natural targets.