We present a multichannel cardiac magnetic field imaging system built in Fribourg from optical double-resonance Cs vapor magnetometers. It consists of 25 individual sensors designed to record magnetic field maps of the beating human heart by simultaneous measurements on a grid of 19 points over the chest. The system is operated as an array of second order gradiometers using sophisticated digitally controlled feedback loops.
We have manufactured more than 250 nominally identical paraffin-coated Cs vapor cells (30 mm diameter bulbs) for multi-channel atomic magnetometer applications. We describe our dedicated cell characterization apparatus. For each cell we have determined the intrinsic longitudinal, Γ 01 , and transverse, Γ 02 , relaxation rates. Our best cell shows Γ 01 /2π ≈ 0.5 Hz, and Γ 02 /2π ≈ 2 Hz. We find a strong correlation of both relaxation rates which we explain in terms of reservoir and spin exchange relaxation. For each cell we have determined the optimal combination of rf and laser powers which yield the highest sensitivity to magnetic field changes. Out of all produced cells, 90% are found to have magnetometric sensitivities in the range of 9 to 30 fT/ √ Hz. Noise analysis shows that the magnetometers operated with such cells have a sensitivity close to the fundamental photon shot noise limit.
ʈWe present a systematic experimental study of the absorption and fluorescence spectra of the 6S 1/2 -6P 1/2 transition in Cs atoms isolated in solid 4 He matrices. The bubble model developed earlier for alkali-metal atoms in liquid He is revised and applied to the present system. The analysis of the dependencies of absorption and fluorescence wavelengths on He pressure in liquid and solid He ͑cubic and hexagonal͒ environments leads us to modify the bubble model by taking the elastic deformation of solid He by the atomic bubble into account.
We present a theoretical and experimental study of the laser-induced formation process and of the emission spectra of Cs * Hen exciplexes in the hcp and bcc phases of solid helium. Two different exciplex molecules are detected: a linear triatomic Cs * He2, which can exist in two electronic states: AΠ 1/2 and BΠ 3/2 , and a larger complex, where 6 or 7 He atoms form a ring around a single cesium atom in the 6P 1/2 state. A theoretical model is presented, which allows the interpretation of the experimentally observed spectra.
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