Bulletin of the American Physical Society
2005 36th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 17–21, 2005; Lincoln, Nebraska
Session K5: Spectroscopy, Lifetime, and Oscillator Strengths |
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Chair: Alan Hibbert, Queen's University Belfast Room: Burnham Yates Conference Center Arbor |
Friday, May 20, 2005 10:30AM - 10:42AM |
K5.00001: Lifetime Measurement of the $8s$ Level in Francium E. Gomez, G. D. Sprouse, L. A. Orozco, A. Perez-Galvan We present a measurement of the lifetime of the 8s level on a magneto-optically trapped sample of $^{210}$Fr atoms using time-correlated single-photon counting. This measurement presents a test for the many body perturbation theory calculations in a strongly relativistic atom. The $8s$ level bears special importance for its possible use in optical parity non- conservation experiments. The $7P_{1/2}$ state serves as the resonant intermediate level in the two-step excitation to the $8s$ level completed with a 1.3 $\mu$m laser. Analysis of the fluorescence decay through the $7P_{3/2}$ level gives the lifetime of the $8s$ level. We complement the study of systematic effects by performing the measurement in the equivalent level in Rb. The final result has an uncertainty of better than 1 \% dominated by statistics and agrees with theoretical calculations. This work is supported by NSF, EG acknowledges support from CONACYT. [Preview Abstract] |
Friday, May 20, 2005 10:42AM - 10:54AM |
K5.00002: Precision Spectroscopy and Density dependant Frequency Shifts in Ultracold Strontium Martin M. Boyd, Tetsuya Ido, Andrew D. Ludlow, Thomas H. Loftus, Jun Ye Cold alkaline earth atoms show great promise as future optical frequency standards and as key components in optical atomic clocks. Atomic strontium is an excellent candidate for a future standard as the level structure allows for both efficient laser cooling to sub-micro Kelvin temperatures and a variety of narrow clock transitions. We report the first high accuracy measurement of the $^{88}$Sr $^{1}$S$_{0}-^{3}$P$_{1}$ clock transition using an ultracold (1uK) sample, yielding a frequency of (434,829,121,312,334 +/-20$_{stat}$ +/-33$_{sys})$ Hz. Detailed descriptions of both the measurement technique and corresponding systematic uncertainties are given. In addition, by varying the density of the ultracold $^{88}$Sr sample over a range of three orders of magnitude we obtain the first definitive measurement of a density-related frequency shift and linewidth broadening of an optical clock transition in an ultracold alkaline earth system. [Preview Abstract] |
Friday, May 20, 2005 10:54AM - 11:06AM |
K5.00003: Testing fundamental constants with trapped indium ions William Trimble, Warren Nagourney The $^1$S$_0 \leftrightarrow ^3$P$_0$ transition in the In$^+$ ion at 237 nm has a natural linewidth of .8 Hz and is a promising candidate for the development of an optical clock. Since this transition is J=0 $\rightarrow$ J=0, the states are not perturbed by the quadrupole trapping potential. We report trapping and spectroscopy of single indium ions using a Paul-Straubel trap and a laser system on the $^1$S$_0 \leftrightarrow ^3$P$_1$ transition at 230 nm and the development of a frequency quadrupled stabilized Nd:YAG laser to excite the narrow $^1$S$_0 \leftrightarrow ^3$P$_0$ transition. We describe prospects for measuring the time-variation of the electromagnetic coupling constant by comparing the frequency of an oscillator locked to the In$^+$ transition to those of other optical clocks. [Preview Abstract] |
Friday, May 20, 2005 11:06AM - 11:18AM |
K5.00004: Observation of the $^{1}$S$_{0}$ -- $^3$P$_0$ clock transition at 578 nm in atomic Yb Tao Hong, Claire Cramer, Eryn Cook, Warren Nagourney, Norval Fortson We report the first observation of the strongly forbidden $6s^2$ $^{1}$S$_{0}$ -- $6s6p$ $^3$P$_0$ transition near 578 nm in atomic Yb, which is weakly† allowed in the odd isotopes ($^{171, 173}$Yb) through internal hyperfine coupling† of the nuclear spin.† This transition has been proposed as one of the† primary† candidates for future optical frequency standards using alkaline earth atoms [1]. In our experiment, a 578 nm laser beam strikes cold Yb atoms† held in a magneto-optical trap (MOT). When this light is tuned to resonance† with the clock transition, a decrease in the MOT fluorescence is detected† as atoms are pumped into the metastable $^3$P$_0$ state and escape† from the trap. By chopping the MOT and clock beams out of phase, we avoid line shifts and broadening due to near-resonant trap light. Nearby 578 nm iodine lines, observed by Doppler-free† saturated absorption, are used as a frequency reference. †We find the $^ {171}$Yb transition to be about $2.5$ GHz below the first hyperfine component of the iodine line 1852. We will present our measurements of the clock transition frequency, including a determination of the relative shift between the $^{171}$Yb and $^{173}$Yb isotopes.[1]S. G.† Porsev, A. Derevianko, E. N. Fortson, Phys. Rev. A {\bf 69}, 021403(R)† (2004); H. Katori, in {\it Proc. 6th Symposium Frequency Standards and Metrology}, edited by P. Gill (World Scienti.c, Singapore, 2002), pp. 323-330 [Preview Abstract] |
Friday, May 20, 2005 11:18AM - 11:30AM |
K5.00005: Physical Model of Modulation Dependent Effects in CPT Clocks Michael Crescimanno, Irina Novikova, David Phillips, Ron Walsworth We report on the semi-analytic evaluation of the three level atom in multiple light fields subject to a slow phase modulation. Combining these results with a model of the corresponding phase sensitive detection leads to a demodulated line shape that quantitatively accounts for the shifts and dependencies that have been observed in systematic studies of Coherent Population Trapping (CPT) resonances.\footnote{to appear in JOSAB, Feb. 2005} Understanding these effects in detail is likely to be of utility in the optimization of miniature atomic time standards based on optical coherences. [Preview Abstract] |
Friday, May 20, 2005 11:30AM - 11:42AM |
K5.00006: Femtosecond Comb Coherent Accumulation and Spectroscopy Matthew Stowe, Adela Marian, John Lawall, Daniel Felinto, Flavio Cruz, Jun Ye The development of phase stabilized modelocked lasers has enabled a revolution in the field of high precision spectroscopy. The light produced by such a broadband laser typically consists of millions of equally spaced modes spanning many tens of nanometers. Once the comb is referenced to a frequency standard the optical frequencies of the laser modes are known with excellent precision. Current applications of femtosecond frequency combs range from atomic clocks and molecular spectroscopy to frequency transfer and high field physics. The technique of multiple pulse coherent accumulation is used to conduct direct frequency comb spectroscopy via one and two photon absorption in cold Rubidium atoms. Femtosecond pulses allow more efficient frequency mixing than with comparable power cw lasers. This fact combined with the narrow comb mode linewidth enables spectroscopy and perhaps cooling of atoms on transitions at traditionally hard to reach wavelengths. [Preview Abstract] |
Friday, May 20, 2005 11:42AM - 11:54AM |
K5.00007: Microwave spectroscopy of Ba 5$d_{3/2}$n$\ell $ autoionizing states E. S. Shuman, T. F. Gallagher By applying microwave fields at frequencies near the $\Delta n=\pm $1 transition we can drive atoms from the autoionizing Ba 5$d_{3/2} $\textit{ng} states to the longer lived 5$d_{3/2}n\pm $1$h$ states. We can accurately determine the quantum defects of both the $g$ and $h$ states by measuring the frequencies at which these transitions occur. Specifically, we have studied $n$'s ranging from 44 to 55 and used frequencies ranging from 40 to 75 GHz. Over this range of $n$ we have determined that the $g$ and $h$ states with the lowest allowed value of J are nearly degenerate and have negative quantum defects. In atoms with anisotropic cores, such as Ba$^{+}$ 5$d_{3/2}$, quadrupole splittings due to the permanent quadrupole moment of the ion core and the quadrupole polarization of the ion core can in fact increase the energy levels more than the dipole polarization depresses them. This results in a negative quantum defect as we observe for the $g$ and $h$ states. We attribute the near degeneracy of these states to the fact that the decrease in the dipole polarization energy is equal to the change in the quadrupole energy with an increase of $\ell $ by one. We believe that this is the first time spectroscopy of autoionizing states using microwaves has been performed. This work has been supported by the U.S. Department of Energy. [Preview Abstract] |
Friday, May 20, 2005 11:54AM - 12:06PM |
K5.00008: X-ray M-shell spectra of multiply-charged heavy ions and their polarization properties Alla Safronova, Ulyana Safronova, Travis Hoppe, Nicholas Ouart, Victor Kantsyrev X-ray M-shell spectra of multiply-charged Ta and W ions are theoretically studied. The details of the atomic structure included in the modeling as well as comparisons with different atomic data codes are presented. Sensitivity of such spectra to the numbers of ionization stages and levels taken into account is discussed. In addition, polarization properties of these spectra are analyzed. In particular, the x-ray line polarization of the prominent M-shell tantalum and tungsten lines is calculated, and polarization markers are identified. X-ray spectropolarimetry is proposed to study polarization of Ta and W line emissions and is illustrated using the results of polarization-sensitive experiments with mid-Z ions. Possible applications to EBIT and plasma experiments are discussed. Work was supported by DOE-NNSA/NV Cooperative Agreement DE-FC52-01NV14050. [Preview Abstract] |
Friday, May 20, 2005 12:06PM - 12:18PM |
K5.00009: Splitting of $\Lambda$-doubling in the transition of Hund's coupling cases in sodium molecule Chin-Chun Tsai, Ray-Yuan Chang, Thou-Jen Whang, Chuen-Ping Cheng The phenomenon of orbital angular momentum $L$-uncoupling from its internuclear axis is observed in Na$_2$ by using high resolution cw optical-optical double resonance spectroscopy. This $L$-uncoupling removes the degeneracy of $\Lambda$-type doubling. In the case of Na$_2$, however, such $\Lambda$-type doubling only reported in the $B\,^1\Pi_u$ state with large speed of rotation and without significant dependence on the vibrational quantum number $v$. In this study, the splitting of $\Lambda$-doubling in the $4\,^1\Pi_g$ and $5\,^1\Delta_g$ states of Na$_2$ is directly measured under our experimental resolution. This splitting caused by the transition of Hund's coupling from case (a) to case (d) is due to $L$-uncoupling from its internuclear axis. The observed energy levels with $e/f$ parities are assigned and the $\Lambda$-type splitting constants $q_0$, $q_v$ and $\mu$ are globally fitted to a standard deviation of $\sigma$ less than $0.03\,cm^{-1}$. [Preview Abstract] |
Friday, May 20, 2005 12:18PM - 12:30PM |
K5.00010: Calculations of liquid helium and neon VUV emission spectra, self-absorption and scattering for a neutrino detector I.M. Savukov To evaluate the feasibility of the recently proposed detection scheme of low energy neutrinos released from the Sun and supernovae called CLEAN, Cryogenic Low Energy Astrophysics with Noble Gases, which relies on the transparency of the noble-gas liquids to VUV radiation produced by neutrinos, we analyze theoretically VUV emission, self-absorption, and scattering of liquid helium and neon, primary candidates for CLEAN. Owing to strong repulsion of noble-gas atoms in the ground state at the equilibrium distance of the relevant excited state, the emission spectrum is substantially shifted from the absorption spectrum, and in principle the absorption is expected very small, allowing building large detectors. Our analysis, however, shows that the self-absorption and Rayleigh scattering are comparable to the size of the proposed detector. [Preview Abstract] |
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K5.00011: Precision lifetime measurements of a single trapped ion with fast laser pulses David Moehring, Martin Madsen, Boris Blinov, Rudolph Kohn, Richard Vallery, David Gidley, Christopher Monroe We report precision measurements of the excited state lifetime of the $^{2}$P$_{1/2}$ and $^{2}$P$_{3/2}$ levels of the atomic Cd$^{+}$ ion. A fast laser pulse (length of order 2 psec) promotes a single trapped Cd$^{+}$ ion to its excited state (lifetime of order 3 nsec). Arrival of the spontaneously emitted photon from the ion is correlated in time with the excitation pulse, and the distribution of time delays from many such events provides the information for the excited state lifetime. By using this technique, we are able to eliminate prevalent systematic errors such as pulse pileup, radiation trapping, flight from view, sub/superradiance, non-selective excitation and/or detection, and potential effects from applied light during the measurement interval. With uncertainties of less than 0.3{\%}, these results are among the most precise measurements of atomic state lifetimes to date. This work is supported by the U.S. National Security Agency and the Advanced Research and Development Activity under Army Research Office contract, and the National Science Foundation ITR program. [Preview Abstract] |
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