S. A. Lee

Light force cooling, focusing, and nanometer-scale deposition of aluminum atoms.

We deposited neutral-aluminum atoms in thin parallel lines to form a grating with a line separation of 154.7 nm by using near-resonant laser light and direct-write optical lithography techniques. We did this by using the single-frequency closed UV transition from the second ground state 3p2P3/2 (F = 4) to 3d2D5/2 (F = 5) at 309.4 nm. The aluminum features were analyzed with an atomic-force microscope.

New measurement of the relativistic Doppler shift in neon

The Doppler free two photon transition from the metastable 1S{sub 5} to 4S{sub 1}{prime}{double_prime} in neon was measured for both a fast beam ({approx}120 keV) and a slow thermal beam. The transition frequencies for each beam were measured independently relative to a hyperfine component of a nearby I{sub 2} reference line. The absolute frequency shift between the two beams was obtained. This measurement of the relativistic Doppler shift verifies the time dilation effect to an accuracy of 2.3 ppm which represents a more than 10 fold improvement over previous measurements.

Measurements of a supersonic velocity in a nitrogen flow using inverse Raman spectroscopy

Results of supersonic molecular flow-velocity measurements using inverse Raman spectroscopy are reported for the first time to our knowledge. Because of potential wind-tunnel applications, flowing N(2) molecules are probed directly, and their flow velocity, temperature, and density are measured. The uncertainties are less than 5% for the velocity measurements and about 10% for the temperature and density measurements. To achieve the quoted precision, I(2) fluorescence, I(2) saturated-absorption, and differential-detection techniques are used to stabilize the probe laser, provide an absolute-frequency reference, and reduce detection noise, respectively.

Continuous-wave Rayleigh–Brillouin-gain spectroscopy in SF 6

We have obtained cw Rayleigh-Brillouin-gain spectra of SF(6) for both forward and backward scattering geometry with high spectral resolution. The spectral resolution is better than 4 MHz, and a Brillouin-frequency shift as small as 42 MHz is clearly resolved. Extension of the present technique to other studies is discussed.

Laboratory measurements of atmospheric temperature and backscatter ratio using a high-spectral-resolution lidar technique

A narrow-band atomic blocking (bandstop) filter capable of high aerosol rejection has been developed for lidar applications. Using this filter, and our proposed new high-spectral-resolution lidar technique, laboratory measurementsof atmospheric temperature and backscatter ratio have been made, with an accuracy of 1 K and +/-3%, respectively.

Flow velocity measurements with stimulated Rayleigh–Brillouin-gain spectroscopy

Using stimulated Rayleigh-Brillouin-gain spectroscopy, we report velocity measurements in an atmospheric-pressure subsonic nitrogen flow with 10% uncertainty. It is shown that the accuracy of the velocity measurements increases with gas pressure, making this spectroscopic technique ideal for measuring velocity and other parameters of high-pressure (>1-atm) atomic or molecular flows.

Fundamental Tests of Special Relativity and the Isotropy of Space

When one considers tests of special relativity and the isotropy of space, the experiment of MICHELSON and MORLEY [1] immediately comes to mind. These scientists might not have anticipated that one hundred years after their landmark experiment, there is an ever increasing interest in the subject. The discovery of the anisotropy in the 3K cosmic blackbody radiation and its subsequent interpretation as due to the earth’s motion through the 3K radiation rest frame [2] makes it interesting to reconsider experiments that can test for the one way speed of light. Indeed, high resolution laser spectroscopy appears to have the most to offer in terms of improved techniques and increased precisian for these tests.

Atom interferometry using Bragg scattering of atoms from standing light waves

The method of Bragg scattering from a standing light wave for splitting atoms coherently into two beams is discussed. An interferometer for atoms is demonstrated by Bragg deflection of a beam of collimated metastable neon atoms from three standing light waves. Possibility of using the interferometer in nanolithography is discussed.

A New Calibration of the Relativistic Doppler Effect in Neon

Publisher Summary This chapter describes a new calibration of the relativistic Doppler effect in neon. It describes an experiment in which the difference between the neon 1s5-4s1 two photon transition in an rf discharge cell and an I2 reference transition have been measured. In a previous experiment, the frequency difference of these two transitions was measured using a 120kV neon fast beam. In Doppler-free two-photon spectroscopy, the first order Doppler shift canceled, leaving the second order Doppler shift to be the dominant term. This shift was a consequence of the time dilation effect in the special theory of relativity. Thus, a measurement of the frequency difference between the cell and the fast beam is a direct measure of the time dilation effect. The main improvement of the experiment described in the chapter over this previous measurement was the use of an intermediate I2 reference, which decoupled the cell measurement from the fast beam measurement. This allowed to carry out a careful study of the systematic effects associated with the discharge cell. The chapter summarizes the results from both these experiments. The two measurements are combined to yield an experimental value for the relativistic Doppler shift.

Rayleigh-Brillouin Gain Spectroscopy in Gases

Over the past decade, we have seen extensive research on and application with Raman gain and other types of coherent Raman spectroscopies. These activities have made clear the advantages of coherent spectroscopy:high signal-to-noise, excellent discrimination from stray light and fluorescence backgrounds, and high spectral resolution. While Raman spectroscopy probes frequency shifts typically 10 cm−1 to 3000 cm−1 from the exciting laser line, information on thermal properties of the medium, which include thermal conductivity, shear and bulk viscosities, and lower-frequency excitations may be obtained from quasi-elastic Rayleigh-Brillouin scattering.