The deceleration of beams of neutral particles possessing an electron spin with time-dependent inhomogeneous magnetic fields is demonstrated experimentally. Half the kinetic energy of a velocity-selected part of a pulsed supersonic beam of hydrogen atoms in the ground state is removed using six pulsed magnetic field stages.

The principle of the equivalence of gravitational and inertial mass is one of the cornerstones of general relativity. Considerable efforts have been made and are still being made to verify its validity. A quantum-mechanical formulation of gravity allows for non-Newtonian contributions to the force which might lead to a difference in the gravitational force on matter and antimatter. While it is widely expected that the gravitational interaction of matter and of antimatter should be identical, this assertion has never been tested experimentally. With the production of large amounts of cold antihydrogen at the CERN Antiproton Decelerator, such a test with neutral antimatter atoms has now become feasible. For this purpose, we have proposed to set up the AEGIS experiment at 0168-583X/$ -see front matter Ó 2007 Published by Elsevier B.V.

We observe the formation of long-range Cs2 Rydberg molecules consisting of a Rydberg and a ground-state atom by photoassociation spectroscopy in an ultracold Cs gas near 6s 1/2 (F =3,4)→np 3/2 resonances (n=26-34). The spectra reveal two types of molecular states recently predicted by D. A. Anderson, S. A. Miller, and G. Raithel [Phys. Rev. A 90, 062518 (2014)]: states bound purely by triplet s-wave scattering with binding energies ranging from 400 MHz at n=26 to 80 MHz at n=34, and states bound by mixed singlet-triplet s-wave scattering with smaller and F -dependent binding energies. The experimental observations are accounted for by an effective Hamiltonian including s-wave scattering pseudopotentials, the hyperfine interaction of the ground-state atom, and the spin-orbit interaction of the Rydberg atom. The analysis enabled the characterization of the role of singlet scattering in the formation of long-range Rydberg molecules and the determination of an effective singlet s-wave scattering length for low-energy electron-Cs collisions.Atoms in Rydberg states of high principal quantum number n are weakly bound systems and are extremely sensitive to their environment. In 1934, Amaldi and Segrè [1] observed the pressure-dependent shift and broadening of the Rydberg series of alkali atoms in a gas cell, an effect which was explained by Fermi [2] as originating from the elastic scattering between slow Rydberg electrons and ground-state atoms within the Rydberg orbit. He modeled the pressure shift using a pseudopotentialwhere a is the scattering length and |Ψ(R)| 2 the probability density of the Rydberg electron at the position R of the neutral perturber. Measurements of pressure shifts in Rydberg states thus provide information on the cross sections of elastic collisions between slow electrons and atoms and molecules [2,3]. Equation (1) implies the existence of oscillating interaction potentials between Rydberg and ground-state atoms [4,5]. A manifestation of such potentials are long-range diatomic molecules in which a ground-state atom having a negative s-wave scattering length is attached to a Rydberg atom at a distance corresponding to an antinode of Ψ(R), as was first pointed out by Greene et al. [6]. Such molecules were first observed experimentally by Bendkowsky et al. [7] following excitation of Rb atoms close to ns 1/2 Rydberg states with n=35-37. Later investigations led to the detection of long-range Rb 2 molecules correlated to np 1/2,3/2 (n=7-12) [8], nd 3/2,5/2 (n=34-40) [9], and nd 3/2,5/2 (n=40-49) [10] dissociation asymptotes and long-range Cs 2 molecules correlated to ns 1/2 (n=31-34) [11] and ns 1/2 (n=37,39,40) [12] asymptotes. The analysis of the experimental data confirmed the overall validity of Eq. (1), revealed contributions from triplet pwave scattering channels, and enabled the determination of triplet s-and p-wave scattering lengths that confirmed theoretical predictions [13].Singlet s-wave scattering lengths are expected to be either positive or much smaller than triplet scattering length...

A three-dimensional trap for Rydberg atoms in selected Stark states has been realized experimentally. H atoms seeded in a supersonic expansion of Ar are excited to the low-field seeking n=30, k=25, |m|=0, 2 Rydberg-Stark states, decelerated from a mean initial velocity of 665 m/s to zero velocity in the laboratory frame and loaded into a three-dimensional electrostatic trap. The motion of the cold Rydberg atom cloud in the trap and the decay of the trapped atoms have been studied by pulsed electric field ionization and imaging techniques.

Articles you may be interested inHigh-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopic study of the two lowest electronic states of the ozone cation O 3 + Assignment of the first five electronic states of Ar 2 + from the rotational fine structure of pulsed-field-ionization zero-kinetic-energy photoelectron spectra Sequences of pulsed electric fields have been designed and tested that enable a higher selectivity in the pulsed field ionization of high Rydberg states (nу100) than has so far been possible. The enhanced selectivity originates from the permutation of the parabolic quantum numbers n 1 and n 2 that is induced by a sufficiently rapid inversion of the electric field polarity during a pulse sequence. A reliable procedure, based on numerical simulations of the outcome of pulse field ionization sequences, has been developed to detect and control changes in the parabolic quantum numbers that can occur during a pulse sequence. The procedure can be used to assess under which conditions a clean permutation of the parabolic quantum numbers can be achieved. Unwanted randomization of m, n 1 and n 2 , which reduces the selectivity of the field ionization process, can be avoided by minimizing the time intervals during which the electric field in the pulse sequence is almost zero. The high selectivity reached in the pulsed field ionization of high Rydberg states has been used to record pulsed-field-ionization zero-kinetic-energy photoelectron spectra of argon and nitrogen at an unprecedented resolution of 0.06 cm Ϫ1 . This resolution opens new perspectives in photoelectron spectroscopy.