Nuclear Transition Probabilities Research Articles

Nuclear excitation cross section of Th229 via inelastic electron scattering

Nuclear excitation cross section of $^{229}\mathrm{Th}$ from the ground state to the low-lying isomeric state via inelastic electron scattering is calculated, on the level of Dirac distorted wave Born approximation. With electron energies below 100 eV, inelastic scattering is very efficient in the isomeric excitation, yielding excitation cross sections on the order of ${10}^{\ensuremath{-}27}$ to ${10}^{\ensuremath{-}26}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}$. Systematic analyses are presented on elements affecting the excitation cross section, including the ion-core potential, the relativistic effect, the knowledge of the reduced nuclear transition probabilities, etc.

Nuclear coherent population transfer to the Th229m isomer using x-ray pulses

Population of the 8 eV $^{229m}$Th isomer via the second nuclear excited state at 29.19 keV by means of coherent x-ray pulses is investigated theoretically. We focus on two nuclear coherent population transfer schemes using partially overlapping x-ray pulses known from quantum optics: stimulated Raman adiabatic passage (STIRAP), and successive $\pi$ pulses. Numerical results are presented for three possible experimental setups. Our results identify the Gamma Factory as the most promising scenario, where two ultraviolet pulses combined with relativistically accelerated ions deliver the required intensities for efficient isomer population. Our simulations require knowledge of the in-band and cross-band nuclear transition probabilities. We give theoretically predicted values for the latter and discuss them in the context of recent experiments.

Electric quadrupole channel of the 7.8 eV Th229 transition

The unique isomeric transition at 7.8 eV in $~^{229}\mathrm{Th}$ has a magnetic dipole ($M1$) and an electric quadrupole ($E2$) multipole mixing. So far, the $E2$ component has been widely disregarded. Here, we investigate the nuclear physics nature and the impact of the $E2$ decay channel for the nuclear coupling to the atomic shell based on the newest theoretical predictions for the corresponding reduced nuclear transition probabilities. Our results show that the contribution of the $E2$ channel is dominant or at least of the same order of magnitude for internal conversion or electronic bridge transitions involving the atomic orbitals $7p$, $6d$ and $5f$. Notable exceptions are the internal conversion of the $7s$ electron and the electronic bridge between the electronic states $7s$ and $7p$, for which the $M1$ component dominates by two to three orders of magnitude. Caution is therefore advised when considering isomeric excitation or decay via nuclear coupling to the atomic shell, as the involved orbitals determine which multipole transition component dominates.

Spectroscopy of cooperative laser–electron nuclear effects in multiatomic molecules

A consistent quantum approach to calculating the electron–nuclear γ transition spectra (a set of vibration–rotational satellites in a molecule) of a nucleus in the multiatomic molecules is proposed and generalizes the well-known Letokhov–Minogin model. Estimates of the vibration–nuclear transition probabilities in a case of the emission and absorption spectrum of nucleus 188Os in the molecule of OsO4 and nucleus 191Ir in the molecule IrO4 are presented.

The time-dependent variational description of nuclear transition probabilities

Abstract A time-averaged gauge invariant wavefunction is considered as a representative for the stationary-state wavefunction of the nuclear collective motion. To verify its accuracy the diagonal and off-diagonal transition probabilities are numerically calculated in three closed-shell nuclei and compared to the corresponding generator coordinate method results. The agreement, even for strongly anharmonic motion, provides strong support for the time-dependent variational description. Thus, this method emerges as an interesting alternative for calculating the nuclear transition probabilities.

Scattering of High-Energy Electrons by Nitrogen-14 and -15

Cross sections of elastic and inelastic electron scattering at incident electron energies of 250 and 400 MeV are presented. Data are given for elastic and inelastic scattering from ${\mathrm{N}}^{15}$ and elastic scattering from ${\mathrm{N}}^{14}$. The data are analyzed with the use of the shell model, in Born approximation. The rms radius of ${\mathrm{N}}^{14}$ is found to be 2.64 F at 400 MeV. The rms radius of ${\mathrm{N}}^{15}$ at 250 and 400 MeV is 2.65 and 2.63 F, respectively. Excited levels in ${\mathrm{N}}^{15}$ at 5.3, 6.3, and 7.3 MeV are studied. Values of the nuclear transition probabilities are presented for these levels. The spin and parity assignments made are ${J}^{\ensuremath{\pi}}={\frac{5}{2}}^{+}$ and ${J}^{\ensuremath{\pi}}={\frac{1}{2}}^{+}$ for the doublet at 5.3 MeV. The 6.3-MeV level is assigned ${J}^{\ensuremath{\pi}}={\frac{3}{2}}^{\ensuremath{-}}$. Of the triplet of levels at 7.3 MeV, only the 7.3- and 7.5-MeV levels are strongly excited. These agree with ${J}^{\ensuremath{\pi}}={\frac{3}{2}}^{+}$ and ${J}^{\ensuremath{\pi}}={\frac{7}{2}}^{+}$, respectively.

Clebsch-Gordan coefficients for nuclear transition probabilities for even-A deformed nuclei

This table has been prepared in order to help calculate alpha-, beta-, and gamma-ray transition probabilities for deformed nuclei. A similar table for odd-mass deformed nuclei was issued before by Lum, Light, and Asaro. In addition to the Clebsch-Gordon coefficients, the squares of the coefficients are also tabulated, since the transition probabilities are proportional to the squares.