Fluorescence-lifetime-limited trapping of Rydberg helium atoms on a chip

Metastable (1s)(2s) S-3(1) helium atoms produced in a supersonic beam were excited to Rydberg-Stark states (with n in the 27-30 range) in a cryogenic environment and subsequently decelerated by, and trapped above, a surface-electrode decelerator. In the trapping experiments, the Rydberg atoms were brought to rest in 75 mu s and over a distance of 33 mm and kept stationary for times t(trap) in the 0-525 mu s range, before being re-accelerated for detection by pulsed field ionisation. The use of a home-built valve producing short gas pulses with a duration of about 20 mu s enabled the reduction of losses arising from collisions with atoms in the trailing part of the gas pulses. Cooling the decelerator to 4.7 K further suppressed losses by transitions induced by blackbody radiation and by collisions with atoms desorbing from the decelerator surface. The main contribution (60%) to the atom loss during deceleration is attributed to the escape out of the decelerator moving traps of atoms having energies higher than the trap saddle point, spontaneous emission and collisions with atoms in the trailing part of the gas pulses causing each only about 20% of the atom loss. At 4.7 K, the atom losses in the trapping phase of the experiments were found to be almost exclusively caused by spontaneous emission and the trap lifetimes were found to correspond to the natural lifetimes of the Rydberg-Stark states. Increasing the temperature to 100 K enhanced the trap losses by transitions stimulated by blackbody radiation. [GRAPHICS]