arXiv subjects

Daniel Kleppner

Publications and source records attributed to Daniel Kleppner.

7 recordsLinked to original sources

arXiv2010

Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with 3He

We have measured the ratio of the diffusion cross-section to the angular momentum reorientation cross-section in the colliding Fe-3He and Ni-3He systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into a cryogenically cooled experimental cell containing cold (< 1 K) 3He buffer gas. Elastic collisions rapidly cool the translational temperature of the ablated atoms to the helium temperature. The cross-section ratio is extracted by measuring the decays of the atomic Zeeman sublevels. For our experimental conditions, thermal energy is comparable to the Zeeman splitting. As a result, thermal excitations between Zeeman sublevels significantly impact the observed decay. To determine the cross-section ratio accurately, we introduce a model of Zeeman state dynamics that includes thermal excitations. We find the cross-section ratio for Ni-3He = 5 x 10^3 and Fe-3He <= 3 x 10^3 at 0.75 K in a 0.8 T magnetic field. These measurements are interpreted in the context of submerged shell suppression of spin relaxation as studied previously in transition metals and rare earth atoms.

physics.atom-ph↗

arXiv2002

Inelastic Collision Rates of Trapped Metastable Hydrogen

We report the first detailed decay studies of trapped metastable (2S) hydrogen. By two-photon excitation of ultracold H samples, we have produced clouds of at least 5x10^7 magnetically trapped 2S atoms at densities greater than 4x10^10 cm^-3 and temperatures below 100 \muK. We derive experimental values for the total 2S-2S two-body loss rate constant in this temperature regime. Our results are in the range of recent theoretical calculations. We also find experimental upper limits on the rate constant for loss due to inelastic 1S-2S collisions.

physics.atom-ph↗

arXiv2000

One Hundred Years of Quantum Physics

On the occasion of the 100th anniversary of the birth of the quantum idea, the development, achievements, and promises of quantum mechanics are described.

quant-ph↗

arXiv1999

Cold Collision Frequency Shift of an Optical Spectrum of a Trapped Gas

We develop an exact sum rule that relates the spectral shift of a trapped gas undergoing cold collisions to measurable quantities of the system. The method demonstrates the dependence of the cold collision frequency shift on the quantum degeneracy of the gas and facilitates extracting scattering lengths from the data. We apply the method to analyzing spectral data for magnetically trapped hydrogen atoms and determine the value of the $1S-2S$ scattering length.

physics.atom-ph↗

arXiv1998

Bose-Einstein Condensation of Atomic Hydrogen

We have observed Bose-Einstein condensation (BEC) of trapped atomic hydrogen, and studied it by two-photon spectroscopy of the 1S-2S transition. In these lecture notes we briefly review the history of spin-polarized atomic hydrogen and describe the final steps to BEC. Laser spectroscopy, which probes the difference in mean field energy of the 1S and 2S states, is used to study the condensate, which has a peak density of 4.8e15 cm^-3 and population of 10^9.

physics.atom-ph↗

arXiv1998

Cold Collision Frequency Shift of the 1S-2S Transition in Hydrogen

We have observed the cold collision frequency shift of the 1S-2S transition in trapped spin-polarized atomic hydrogen. We find $Δν_{1S-2S} = -3.8(8)\times 10^{-10} n Hz cm^3$, where $n$ is the sample density. From this we derive the 1S-2S s-wave triplet scattering length, $a_{1S-2S}=-1.4(3)$ nm, which is in fair agreement with a recent calculation. The shift provides a valuable probe of the distribution of densities in a trapped sample.

physics.atom-ph↗

arXiv1998

Bose-Einstein Condensation of Atomic Hydrogen

We report observation of Bose-Einstein condensation of a trapped, dilute gas of atomic hydrogen. The condensate and normal gas are studied by two-photon spectroscopy of the 1S-2S transition. Interactions among the atoms produce a shift of the resonance frequency proportional to density. The condensate is clearly distinguished by its large frequency shift. The peak condensate density is 4.8 +/- 1.1 \times 10^{15} cm^{-3}, corresponding to a condensate population of 10^9 atoms. The BEC transition occurs at about T=50 uK and n=1.8 \times 10^{14} cm^{-3}.

physics.atom-ph↗