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Events on Tuesday, December 7th, 2010

Atomic Physics Seminar
Measurement of the dipole moment for transitions to Rydberg states in ultracold rubidium
Time: 11:00 am
Place: 5280 Chamberlin
Speaker: Michal Piotrowicz, The Open University, Milton Keynes UK
Abstract: Dipole matrix elements are required for calculations of numerous spectroscopic properties of excited atoms including oscillator strengths, polarisabilities and radiative lifetimes. There is no exact analytical solution for the calculation of radial matrix elements for alkali atoms, however many theoretical models have been developed that include numeric integration of Schroedinger's equation in the Coulomb approximation with quantum defects taken as input parameters or using various model potentials. In quasiclassical methods the radial matrix elements are calculated avoiding the direct numerical integration using transcendental functions. Despite the large number of existing theoretical models, lack of experimental data on dipole matrix elements for rubidium complicates their verification.

In my talk I will present the experimental setup built at The Open University, UK to investigate the ultracold Rydberg atoms. I will show our first results of the measurements of the dipole moments for the transitions to the Rydberg states by investigation of the electromagnetically induced transparency (EIT) in ultracold 87Rb gas. The absorption profile of a weak probe laser beam on 5S1/2 → 5P3/2 transition is observed in the presence of a strong coupling laser beam at 480 nm driving the 5P3/2nD5/2 transition for the Rydberg states with principal quantum numbers in the range 20≤n≤48. The strong dependence of the shape of the EIT spectrum on the Rabi frequency of the transition between the first excited state and Rydberg states allowed us to directly measure the dipole moments of the transitions involved for several values of principal number n.

The dipole matrix elements for transitions measured in our experiment are compared with theoretical methods including quasiclassical calculations based on Dyachkov-Pankratov model, and Coulomb approximations. A very good agreement with the theoretical calculations is observed.

I will conclude the talk with the outline of further projects with ultracold Rydberg atoms that are carried out at the Open University.
Host: Mark Saffman
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String Theory Seminar
Title to be announced
Time: 4:00 pm
Place: 5280 Chamberlin Hall
Speaker: Fernando Marchesano, IFT Madrid
Host: Shiu
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