Calculation of isotope shifts and relativistic shifts in CI, CII, CIII and CIV

We present an accurate ab initio method of calculating isotope shifts and relativistic shifts in atomic spectra. We test the method on neutral carbon and three carbon ions. The relativistic shift of carbon lines may allow them to be included in analyses of quasar absorption spectra that seek to measure possible variations in the fine structure constant, alpha, over the lifetime of the Universe. Carbon isotope shifts can be used to measure isotope abundances in gas clouds: isotope abundances are potentially an important source of systematic error in the alpha-variation studies. These abundances are also needed to study nuclear reactions in stars and supernovae, and test models of chemical evolution of the Universe

Polarization dependent photoionization cross-sections and radiative lifetimes of atomic states in Ba

The photoionization cross-sections of two even-parity excited states, $5d6d ^3D_1$ and $6s7d ^3D_{2}$, of atomic Ba at the ionization-laser wavelength of 556.6 nm were measured. We found that the total cross-section depends on the relative polarization of the atoms and the ionization-laser light. With density-matrix algebra, we show that, in general, there are at most three parameters in the photoionization cross-section. Some of these parameters are determined in this work. We also present the measurement of the radiative lifetime of five even-parity excited states of barium.Comment: 11 pages, 7 figure

Isotope shifts and hyperfine structure of the Fe I 372 nm resonance line

We report measurements of the isotope shifts of the $3d^64s^2 a ^5D_4 - 3d^64s4p z ^5F_5^o$ Fe I resonance line at 372 nm between all four stable isotopes $^{54}$Fe, $^{56}$Fe, $^{57}$Fe, and $^{58}$Fe, as well as the complete hyperfine structure of that line for $^{57}$Fe, the only stable isotope having a non-zero nuclear spin. The field and specific mass shift coefficients of the transition have been derived from the data, as well as the experimental value for the hyperfine structure magnetic dipole coupling constant $A$ of the excited state of the transition in $^{57}$Fe: $A(3d^64s4p z ^5F_5^o) = 81.69(86)$ MHz. The measurements were done by means of Doppler-free laser saturated-absorption spectroscopy in a Fe-Ar hollow cathode using both natural and enriched iron samples. The measured isotope shifts and hyperfine constants are reported with uncertainties at the percent level.Comment: 5 pages, 5 figure

Investigation of cold Rb Rydberg atoms in a magneto-optical trap

We present our results on the experiments with cold Rb Rydberg atoms in a magneto-optical trap (MOT). Characteristic features of our experiment were the excitation of Rydberg atoms in a small volume within the cold atom cloud and sorting of the measured signals and spectra over the number of registered Rydberg atoms. We have measured the effective lifetime of the Rydberg state 37P, as well as its polarizability in a weak electric field. The results are in good agreement with the theoretical calculations. We have shown that localization of the small excitation volume around the zero-magnetic-field point makes possible to increase the spectral resolution and to obtain narrow microwave resonances in Rydberg atoms without switching off the MOT quadrupole magnetic field. We have measured the dependence of the amplitude of the dipole-dipole interaction resonances on the number of Rydberg atoms, which has a linear character and agrees with the theory for weak dipole-dipole interaction.Comment: 9 pages, 6 figures. To appear in JETP, 2009. Typo in eq.(7) corrected in v

Collisional perturbation of radio-frequency E1 transitions in an atomic beam of dysprosium

We have studied collisional perturbations of radio-frequency (rf) electric-dipole (E1) transitions between the nearly degenerate opposite-parity levels in atomic dysprosium (Dy) in the presence of 10 to 80 $\mu$Torr of H$_\text{2}$, N$_\text{2}$, He, Ar, Ne, Kr, and Xe. Collisional broadening and shift of the resonance, as well as the attenuation of the signal amplitude are observed to be proportional to the foreign-gas density with the exception of H$_2$ and Ne, for which no shifts were observed. Corresponding rates and cross sections are presented. In addition, rates and cross sections for O$_2$ are extracted from measurements using air as foreign gas. The primary motivation for this study is the need for accurate determination of the shift rates, which are needed in a laboratory search for the temporal variation of the fine-structure constant [A. T. Nguyen, D. Budker, S. K. Lamoreaux, and J. R. Torgerson, Phys. Rev. A \textbf{69}, 22105 (2004)].Comment: 11 pages, 8 figure

Broadening and intensity redistribution in the Na(3p3p) hyperfine excitation spectra due to optical pumping in the weak excitation limit

Detailed analysis of spectral line broadening and variations in relative intensities of hyperfine spectral components due to optical pumping is presented. Hyperfine levels of sodium $3p_{1/2}$ and $3p_{3/2}$ levels are selectively excited in a supersonic beam at various laser intensities under the conditions when optical pumping time is shorter than transit time of atoms through the laser beam. The excitation spectra exhibit significant line broadening at laser intensities well below the saturation intensity, and redistribution of intensities of hyperfine spectral components is observed, which in some cases is contradicting with intuitive expectations. Theoretical analysis of the dynamics of optical pumping shows that spectral line broadening depends sensitively on branching coefficient of the laser-driven transition. Analytical expressions for branching ratio dependent critical Rabi frequency and critical laser intensity are derived, which give the threshold for onset of noticeable line broadening by optical pumping. Transitions with larger and smaller branching coefficients are relatively less affected. The theoretical excitation spectra were calculated numerically by solving density matrix equations of motion using the split propagation technique, and they well reproduce the observed effects of line broadening and peak intensity variations. The calculations also show that presence of dark (i.e., not laser- coupled) Zeeeman sublevels in the lower state results in effective branching coefficients which vary with laser intensity and differ from those implied by the sum rules, and this can lead to peculiar changes in peak ratios of hyperfine components of the spectra.Comment: 12 pages, 10 figure

Atom made from charged elementary black hole

It is believed that there may have been a large number of black holes formed in the very early universe. These would have quantised masses. A charged ``elementary black hole'' (with the minimum possible mass) can capture electrons, protons and other charged particles to form a ``black hole atom''. We find the spectrum of such an object with a view to laboratory and astronomical observation of them, and estimate the lifetime of the bound states. There is no limit to the charge of the black hole, which gives us the possibility of observing Z>137 bound states and transitions at the lower continuum. Negatively charged black holes can capture protons. For Z>1, the orbiting protons will coalesce to form a nucleus (after beta-decay of some protons to neutrons), with a stability curve different to that of free nuclei. In this system there is also the distinct possibility of single quark capture. This leads to the formation of a coloured black hole that plays the role of an extremely heavy quark interacting strongly with the other two quarks. Finally we consider atoms formed with much larger black holes.Comment: 22 pages, 4 figure

Fine and hyperfine structure of the muonic ^3He ion

On the basis of quasipotential approach to the bound state problem in QED we calculate the vacuum polarization, relativistic, recoil, structure corrections of orders $\alpha^5$ and $\alpha^6$ to the fine structure interval $\Delta E^{fs}=E(2P_{3/2})-E(2P_{1/2})$ and to the hyperfine structure of the energy levels $2P_{1/2}$ and $2P_{3/2}$ in muonic $^3_2He$ ion. The resulting values $\Delta E^{fs}= 144803.15 \mu eV$, $\Delta \tilde E^{hfs}(2P_{1/2})=-58712.90 \mu eV$, $\Delta \tilde E^{hfs}(2P_{3/2})=-24290.69 \mu eV$ provide reliable guidelines in performing a comparison with the relevant experimental data.Comment: 15 pages, 4 figures, 3 table