arXiv subjects

G. W. F. Drake

Publications and source records attributed to G. W. F. Drake.

24 records · Page 2Linked to original sources

arXiv2005

Nuclear Charge Radius of Li-9, Li-11: Halo Neutron: the influence of Halo Neutrons

The nuclear charge radius of Li-11 has been determined for the first time by high precision laser spectroscopy. On-line measurements at TRIUMF-ISAC yielded a Li-7 - Li-11 isotope shift (IS) of 25101.23(13) MHz for the Doppler-free 2s - 3s transition. IS precision for all other bound Li isotopes was also improved. Differences from calculated mass-based IS yield values for change in charge radius along the isotope chain. The charge radius decreases monotonically from Li-6 to Li-9, and then increases from 2.217(35) fm to 2.467(37) fm for Li-11. This is compared to various models, and it is found that a combination of halo neutron correlation and intrinsic core excitation best reproduces the experimental results.

physics.atom-ph↗

arXiv2004

Laser Spectroscopic Determination of the 6He Nuclear Charge Radius

We have performed precision laser spectroscopy on individual 6He (t1/2 = 0.8 s) atoms confined and cooled in a magneto-optical trap, and measured the isotope shift between 6He and 4He to be 43,194.772 +/- 0.056 MHz for the 2 3S1 - 3 3P2 transition. Based on this measurement and atomic theory, the nuclear charge radius of 6He is determined, for the first time in a method independent of nuclear models, to be 2.054 +/- 0.014 fm. The result is compared with the values predicted by a number of nuclear structure calculations, and tests their ability to characterize this loosely bound, halo nucleus.

nucl-ex↗

arXiv2004

Fine Structure of the 1s3p ^3P_J Level in Atomic ^4He: Theory and Experiment

We report on a theoretical calculation and a new experimental determination of the 1s3p ^3P_J fine structure intervals in atomic ^4He. The values from the theoretical calculation of 8113.730(6) MHz and 658.801(6) MHz for the nu_{01} and nu_{12} intervals, respectively, disagree significantly with previous experimental results. However, the new laser spectroscopic measurement reported here yields values of 8113.714(28) MHz and 658.810(18) MHz for these intervals. These results show an excellent agreement with the theoretical values and resolve the apparent discrepancy between theory and experiment.

physics.atom-ph↗

arXiv2003

The 2S-2P Lamb Shift in He+

The current theoretical status of the Lamb shift in He+ is discussed. Recent calculations of two-loop binding corrections to the Lamb shift significantly shift the theoretical value of the "classic" Lamb shift in He+, i.e. of the 2S_1/2-2P_1/2-interval. In this brief research note, we present a new (theoretical) value for this interval which reads 14041.474(42) Mhz. The theoretical uncertainty is reduced as well as the discrepancy between theory and experiment. Planned measurements should be of help in further elucidating the situation.

physics.atom-ph↗

arXiv2003

Relativistic and QED energy shifts in positronium ion

The leading relativistic and QED corrections to the ground state energy of the three-body system (epe) are calculated numerically using a Hylleraas correlated basis set. The accuracy of the nonrelativistic variational ground state wave function is discussed with respect to the convergence properties at the increase of the basis dimension and to the variance of the energy expectation value. Recent progress in the numerical procedure used to calculate expectation values for products of various physical operators is presented. It is shown that the nonrelativistic ground state energy can be calculated with an accuracy below the level width. The corrections to this energy include the lowest order Breit interaction, the vacuum polarization potential, one and two photon exchange contributions, the annihilation interaction, and spin-spin contact terms. The relativistic effects and the residual interactions considered here decrease the one electron binding energy from the nonrelativistic value of 0.012 005 070 232 980 10(3) a.u. to 0.011 981 051 246(2) a.u..

physics.atom-ph↗

arXiv1996

Variational calculations of dispersion coefficients for interactions between H, He, and Li atoms

The dispersion coefficients $C_6$, $C_8$, and $C_{10}$ for the interactions between H, He, and Li are calculated using variational wave functions in Hylleraas basis sets with multiple exponential scale factors. With these highly correlated wave functions, significant improvements are made upon previous calculations and our results provide definitive values for these coefficients.

atom-ph↗