Aakash Ravi

Radio Frequency Magneto-Optical Trapping of CaF with High Density

We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields. The rf magneto-optical trap (MOT) confines 1.0(3)×10^{5} CaF molecules at a density of 7(3)×10^{6}  cm^{-3}, which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of 340(20)  μK are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation.

Buffer gas loaded magneto-optical traps for Yb, Tm, Er and Ho

Direct loading of lanthanide atoms into magneto-optical traps (MOTs) from a very slow cryogenic buffer gas beam source is achieved, without the need for laser slowing. The beam source has an average forward velocity of 60– and a velocity half-width of , which allows for direct MOT loading of Yb, Tm, Er and Ho. Residual helium background gas originating from the beam results in a maximum trap lifetime of about 80 ms (with Yb). The addition of a single-frequency slowing laser applied to the Yb in the buffer gas beam increases the number of trapped Yb atoms to with a loading rate of . Decay to metastable states is observed for all trapped species and decay rates are measured. Extension of this approach to the loading of molecules into a MOT is discussed.

ν4band of CH4in helium nanodroplets: A probe of the dynamical response of a superfluid

The triply degenerate {nu}{sub 4} bending mode of methane in superfluid helium nanodroplets was observed at 7.7 {mu}m by high-resolution infrared depletion spectroscopy. Five rotational transitions were detected, with a minimum linewidth of only 65 MHz. The observed lines showed slightly asymmetric line shapes, especially in the case of the P(2) and R(1) rotational lines. Analysis of the line shape indicates that the superfluid environment has a finite response time of a few nanoseconds to equilibrate upon rotational excitation of CH{sub 4}.

Astro-comb calibrator and spectrograph characterization using a turn-key laser frequency comb

Abstract. Using a turn-key Ti:sapphire femtosecond laser frequency comb, an off-the-shelf supercontinuum device and Fabry-Perot mode filters, we report the generation of a 16-GHz frequency comb spanning a 90-nm band about a center wavelength of 566 nm. The light from this astro-comb is used to calibrate the HARPS-N astrophysical spectrograph for precision radial velocity measurements. The comb-calibrated spectrograph achieves a stability of ∼1  cm/s within half an hour of averaging time. We also use the astro-comb as a reference for measurements of solar spectra obtained with a compact telescope and as a tool to study intrapixel sensitivity variations on the spectrograph detector.

Ro-vibrational Spectra of (para-H2 )N -CH4 in He Droplets.

In this work, we report on the infrared spectroscopic study of clusters of CH4 molecules with up to N=80 para-hydrogen molecules assembled inside He droplets. Upon increase of the number of the added para-hydrogen molecules up to about N=12, both the rotational constant, B, and the origin frequency of the υ3 band of CH4 decrease gradually. In the range of 6 ≤N≤12, the spectra indicate some abrupt changes of B and υ3 with both values being approximately constant at N≥12. The origin of this effect is discussed. Comparison of the spectra of methane molecules in para-hydrogen clusters to that in solid para-hydrogen is also presented.