Roland Wester

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Ultracold LiCs molecules in the absolute ground state X1Sigma+, v'' = 0, J'' = 0 are formed via a single photoassociation step starting from laser-cooled atoms. The selective production of v'' = 0, J'' = 2 molecules with a 50-fold higher rate is also demonstrated. The rotational and vibrational state of the ground state molecules is determined in a setup(More)
Anion-molecule nucleophilic substitution (S(N)2) reactions are known for their rich reaction dynamics, caused by a complex potential energy surface with a submerged barrier and by weak coupling of the relevant rotational-vibrational quantum states. The dynamics of the S(N)2 reaction of Cl- + CH3I were uncovered in detail by using crossed molecular beam(More)
We present an accurate potential energy curve of the B (1)Pi state in the LiCs molecule for which vibrational levels between v(') = 0 and v(') = 35 (bound by 11.4 GHz) were measured by photoassociation spectroscopy in an ultracold ensemble of (7)Li and (133)Cs atoms. By the combination of conventional spectroscopic data of the B-X system and the new(More)
Solvents have a profound influence on chemical reactions in solution and have long been used to control their outcome. Such effects are generally considered to be governed by thermodynamics; however, little is known about the steric effects of solvent molecules. Here, we probe the influence of individual solvent molecules on reaction dynamics and present(More)
The energy-resolved rate coefficient for the dissociative recombination (DR) of H(3)(+) with slow electrons has been measured by the storage-ring method using an ion beam produced from a radiofrequency multipole ion trap, employing buffer-gas cooling at 13 K. The electron energy spread of the merged-beams measurement is reduced to 500 microeV by using a(More)
Multipole radiofrequency ion traps are a highly versatile tool to study molecular ions and their interactions in a well-controllable environment. In particular the cryogenic 22-pole ion trap configuration is used to study ion-molecule reactions and complex molecular spectroscopy at temperatures between few Kelvin and room temperatures. This article presents(More)
Absolute total photodetachment cross sections of O(-) and OH(-) anions stored in a multipole radio frequency trap have been measured using a novel laser depletion tomography method. For OH(-) the total cross sections of 8.5(1)(stat)(3)(syst) and 8.1(1)(stat)(7)(syst)x10(-18) cm(2), measured at 662 and 632 nm, respectively, were found constant in the(More)
Infrared absorption spectroscopy of few hundred H+(3) ions trapped in a 22-pole ion trap is presented using chemical probing as a sensitive detection technique down to the single ion level. By exciting selected overtone transitions of the (v(1)=0,v(2) (l)=3(1))<--(0,0(0)) vibrational band using an external cavity diode laser an accurate diagnostics(More)
We identify plain evaporation of ions as the fundamental loss mechanism out of a multipole ion trap. Using thermalized negative Cl- ions we find that the evaporative loss rate is proportional to a Boltzmann factor. This thermodynamic description allows us to extract the effective depth of the ion trap. As a function of the rf amplitude we find two distinct(More)