Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.

Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

We show that light-induced atom desorption ͑LIAD͒ can be used as a flexible atomic source for large 87 Rb and 40 K magneto-optical traps. The use of LIAD at short wavelengths allows for fast switching of the desired vapor pressure and permits experiments with long trapping and coherence times. The wavelength dependence of the LIAD effect for both species was explored in a range from 630 to 253 nm in an uncoated quartz cell and a stainless steel chamber. Only a few mW/ cm 2 of near-UV light produce partial pressures that are high enough to saturate a magneto-optical trap at 3.5ϫ 10 K atoms/s were achieved without the use of a secondary atom source. After the desorption light is turned off, the pressure quickly decays back to equilibrium with a time constant as short as 200 s, allowing for long trapping lifetimes after the MOT loading phase.

Photoionization of triply charged titanium ions was investigated using the merged photon–ion beam technique at a synchrotron light source. The experimental photon energy range 42.6–49.4 eV encompasses the threshold for the photoionization of Ti3+(3p6 3d2 D3/2) ground-state ions at 43.267 eV. Prominent resonance features due to 3p → 3d and 3p → 4s excitations are observed with the strongest one being the ‘giant’ 3p5(3d23F)2F dipole resonance which has a width of 1.5 eV. Since it is located only 0.2 eV above the ionization threshold a cut-off of this resonance is observed in photoionization. By employing the principle of detailed balance the results are compared with an earlier experimental study of the time-reversed Ti4+ photorecombination. The comparison clarifies the giant resonance's role in photorecombination and yields state-selective photoionization and photorecombinaton cross sections on an absolute scale.

No abstract