Detailed studies of non-linear magneto-optical resonances at D1 excitation of Rb-85 and Rb-87 for partially resolved hyperfine F-levels

Experimental signals of non-linear magneto-optical resonances at D1 excitation of natural rubidium in a vapor cell have been obtained and described with experimental accuracy by a detailed theoretical model based on the optical Bloch equations. The D1 transition of rubidium is a challenging system to analyze theoretically because it contains transitions that are only partially resolved under Doppler broadening. The theoretical model took into account all nearby transitions, the coherence properties of the exciting laser radiation, and the mixing of magnetic sublevels in an external magnetic field and also included averaging over the Doppler profile. Great care was taken to obtain accurate experimental signals and avoid systematic errors. The experimental signals were reproduced very well at each hyperfine transition and over a wide range of laser power densities, beam diameters, and laser detunings from the exact transition frequency. The bright resonance expected at the F_g=1 --> F_e=2 transition of Rb-87 has been observed. A bright resonance was observed at the F_g=2 --> F_e=3 transition of Rb-85, but displaced from the exact position of the transition due to the influence of the nearby F_g=2 --> F_e=2 transition, which is a dark resonance whose contrast is almost two orders of magnitude larger than the contrast of the bright resonance at the F_g=2 --> F_e=3 transition. Even in this very delicate situation, the theoretical model described in detail the experimental signals at different laser detunings.Comment: 11 pages, 9 figure

Conversion of bright magneto-optical resonances into dark at fixed laser frequency for D2 excitation of atomic rubidium

Nonlinear magneto-optical resonances on the hyperfine transitions belonging to the D2 line of rubidium were changed from bright to dark resonances by changing the laser power density of the single exciting laser field or by changing the vapor temperature in the cell. In one set of experiments atoms were excited by linearly polarized light from an extended cavity diode laser with polarization vector perpendicular to the light's propagation direction and magnetic field, and laser induced fluorescence (LIF) was observed along the direction of the magnetic field, which was scanned. A low-contrast bright resonance was observed at low laser power densities when the laser was tuned to the Fg=2 --> Fe=3 transition of Rb-87 and near to the Fg=3 --> Fe=4 transition of Rb-85. The bright resonance became dark as the laser power density was increased above 0.6mW/cm2 or 0.8 mW/cm2, respectively. When the Fg=2 --> Fe=3 transition of Rb-87 was excited with circularly polarized light in a second set of experiments, a bright resonance was observed, which became dark when the temperature was increased to around 50C. The experimental observations at room temperature could be reproduced with good agreement by calculations based on a theoretical model, although the theoretical model was not able to describe measurements at elevated temperatures, where reabsorption was thought to play a decisive role. The model was derived from the optical Bloch equations and included all nearby hyperfine components, averaging over the Doppler profile, mixing of magnetic sublevels in the external magnetic field, and a treatment of the coherence properties of the exciting radiation field.Comment: 9 pages, 7 figure

Level-crossing spectroscopy of the 7, 9, and 10D_5/2 states of 133Cs and validation of relativistic many-body calculations of the polarizabilities and hyperfine constants

We present an experimental and theoretical investigation of the polarizabilities and hyperfine constants of D_J states in 133Cs for J=3/2 and J=5/2. New experimental values for the hyperfine constant A are obtained from level-crossing signals of the (7,9,10)D_5/2 states of 133Cs and precise calculations of the tensor polarizabilities alpha_2. The results of relativistic many-body calculations for scalar and tensor polarizabilities of the (5-10)D_3/2 and (5-10)D_5/2 states are presented and compared with measured values from the literature. Calculated values of the hyperfine constants A for these states are also presented and checked for consistency with experimental values.Comment: 12 pages, revtex4, 11 figure file

Comparison of alternate scoring of variables on the performance of the frailty index

Background: The frailty index (FI) is used to measure the health status of ageing individuals. An FI is constructed as the proportion of deficits present in an individual out of the total number of age-related health variables considered. The purpose of this study was to systematically assess whether dichotomizing deficits included in an FI affects the information value of the whole index. Methods: Secondary analysis of three population-based longitudinal studies of community dwelling individuals: Nova Scotia Health Survey (NSHS, n = 3227 aged 18+), Survey of Health, Ageing and Retirement in Europe (SHARE, n = 37546 aged 50+), and Yale Precipitating Events Project (Yale-PEP, n = 754 aged 70+). For each dataset, we constructed two FIs from baseline data using the deficit accumulation approach. In each dataset, both FIs included the same variables (23 in NSHS, 70 in SHARE, 33 in Yale-PEP). One FI was constructed with only dichotomous values (marking presence or absence of a deficit); in the other FI, as many variables as possible were coded as ordinal (graded severity of a deficit). Participants in each study were followed for different durations (NSHS: 10 years, SHARE: 5 years, Yale PEP: 12 years). Results: Within each dataset, the difference in mean scores between the ordinal and dichotomous-only FIs ranged from 0 to 1.5 deficits. Their ability to predict mortality was identical; their absolute difference in area under the ROC curve ranged from 0.00 to 0.02, and their absolute difference between Cox Hazard Ratios ranged from 0.001 to 0.009. Conclusions: Analyses from three diverse datasets suggest that variables included in an FI can be coded either as dichotomous or ordinal, with negligible impact on the performance of the index in predicting mortality.Fernando G Peña, Olga Theou, Lindsay Wallace, Thomas D Brothers, Thomas M Gill, Evelyne A Gahbauer, Susan Kirkland, Arnold Mitnitski and Kenneth Rockwoo

Nonlinear magneto-optical resonances at D1 excitation of 85Rb and 87Rb in an extremely thin cell

Nonlinear magneto-optical resonances have been measured in an extremely thin cell (ETC) for the D1 transition of rubidium in an atomic vapor of natural isotopic composition. All hyperfine transitions of both isotopes have been studied for a wide range of laser power densities, laser detunings, and ETC wall separations. Dark resonances in the laser induced fluorescence (LIF) were observed as expected when the ground state total angular momentum F_g was greater than or equal to the excited state total angular momentum F_e. Unlike the case of ordinary cells, the width and contrast of dark resonances formed in the ETC dramatically depended on the detuning of the laser from the exact atomic transition. A theoretical model based on the optical Bloch equations was applied to calculate the shapes of the resonance curves. The model averaged over the contributions from different atomic velocity groups, considered all neighboring hyperfine transitions, took into account the splitting and mixing of magnetic sublevels in an external magnetic field, and included a detailed treatment of the coherence properties of the laser radiation. Such a theoretical approach had successfully described nonlinear magneto-optical resonances in ordinary vapor cells. Although the values of certain model parameters in the ETC differed significantly from the case of ordinary cells, the same physical processes were used to model both cases. However, to describe the resonances in the ETC, key parameters such as the transit relaxation rate and Doppler width had to be modified in accordance with the ETC's unique features. Agreement between the measured and calculated resonance curves was satisfactory for the ETC, though not as good as in the case of ordinary cells.Comment: v2: substantial changes and expanded theoretical model; 13 pages, 10 figures; accepted for publication in Physical Review

The GAPS Experiment to Search for Dark Matter using Low-energy Antimatter

The GAPS experiment is designed to carry out a sensitive dark matter search by measuring low-energy cosmic ray antideuterons and antiprotons. GAPS will provide a new avenue to access a wide range of dark matter models and masses that is complementary to direct detection techniques, collider experiments and other indirect detection techniques. Well-motivated theories beyond the Standard Model contain viable dark matter candidates which could lead to a detectable signal of antideuterons resulting from the annihilation or decay of dark matter particles. The dark matter contribution to the antideuteron flux is believed to be especially large at low energies (E < 1 GeV), where the predicted flux from conventional astrophysical sources (i.e. from secondary interactions of cosmic rays) is very low. The GAPS low-energy antiproton search will provide stringent constraints on less than 10 GeV dark matter, will provide the best limits on primordial black hole evaporation on Galactic length scales, and will explore new discovery space in cosmic ray physics. Unlike other antimatter search experiments such as BESS and AMS that use magnetic spectrometers, GAPS detects antideuterons and antiprotons using an exotic atom technique. This technique, and its unique event topology, will give GAPS a nearly background-free detection capability that is critical in a rare-event search. GAPS is designed to carry out its science program using long-duration balloon flights in Antarctica. A prototype instrument was successfully flown from Taiki, Japan in 2012. GAPS has now been approved by NASA to proceed towards the full science instrument, with the possibility of a first long-duration balloon flight in late 2020. Here we motivate low-energy cosmic ray antimatter searches and discuss the current status of the GAPS experiment and the design of the payload.Comment: 8 pags, 3 figures, Proc. 35th International Cosmic Ray Conference (ICRC 2017), Busan, Kore

Accelerator Testing of the General Antiparticle Spectrometer, a Novel Approach to Indirect Dark Matter Detection

We report on recent accelerator testing of a prototype general antiparticle spectrometer (GAPS). GAPS is a novel approach for indirect dark matter searches that exploits the antideuterons produced in neutralino-neutralino annihilations. GAPS captures these antideuterons into a target with the subsequent formation of exotic atoms. These exotic atoms decay with the emission of X-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. This signature uniquely characterizes the antideuterons. Preliminary analysis of data from a prototype GAPS in an antiproton beam at the KEK accelerator in Japan has confirmed the multi-X-ray/pion star topology and indicated X-ray yields consistent with prior expectations. Moreover our success in utilizing solid rather than gas targets represents a significant simplification over our original approach and offers potential gains in sensitivity through reduced dead mass in the target area.Comment: 18 pages, 9 figures, submitted to JCA