Helium-Droplet-Assisted Preparation of Cold RbSr Molecules

Abstract

We present a combined experimental and theoretical study of the RbSr molecule. The experimental approach is based on the formation of RbSr molecules on helium nanodroplets. Utilizing two-photon ionization spectroscopy, an excitation spectrum ranging from 11,600 up to 23,000 cm(-1) was recorded. High level ab initio calculations of potential energy curves and transition dipole moments accompany the experiment and facilitate an assignment of transitions. We show that RbSr molecules desorb from the helium droplets upon excitation, which enables dispersed fluorescence spectroscopy of free RbSr. These spectra elucidate X(2)Σ(+) ground and excited state properties. Emission spectra originating from states corresponding to the Rb(5s(2)S) + Sr(5s5p(3)P) asymptote were recorded; spin-orbit coupling was included for the simulation. The results should provide a good basis for achieving the formation of this molecule in cold collisions, thus offering intriguing prospects for ultracold molecular physics.

The RbSr2Σ+ground state investigatedviaspectroscopy of hot and ultracold molecules

“…Experimental investigation of RbSr has been restricted so far to Helium-nanodroplet-assisted spectroscopy [40,41]. In these experiments a supersonic jet of He droplets is sequentially injected into pickup cells containing Rb or Sr, which can get caught on the droplet surface and reactively collide forming a RbSr molecule.…”

Predissociation dynamics of lithium iodide

“…For our pump-probe experiment, refined detection schemes such as ion imaging techniques would allow to unequivocally confirm suppression of coherent wave packet motion. More generally, it would also be interesting to see whether the regime of intermediate coupling between molecule and He droplet can be explored by using different molecular species, e. g. alkaliearth alkaline mixtures [50]. This would provide much needed input for the theoretical modeling of the interaction of molecules with He droplets and thus be crucial for developing a rigorous understanding of quantum fluid environments.…”

Synthesis of nanoparticles in helium droplets—A characterization comparing mass-spectra and electron microscopy data

“…4,5 The unique properties of He N have enabled fascinating experiments [6][7][8][9][10] and the helium droplet technique has matured to a standard method in spectroscopy of atoms and small molecules. 11,12 Very recently, the method has been applied for the deposition of nanometer-sized metal clusters on surfaces, 13 and later, vortices inside He N were deliberately used to create onedimensional nano-structures. [14][15][16] The size of the produced clusters depends on the doping conditions as well as the mean helium droplet size.…”

“…12,[24][25][26] With TOF mass spectrometers (TOFMSs), it is possible to observe clusters in a size range (consisting of several hundred atoms) [27][28][29] which is also accessible with TEM, enabling a comparison of the two methods.…”

“…The droplets can be sequentially doped using different sources (4,5,6). As diagnostic tools, TOFMS (10), substrates for ex situ TEM investigations (11), and quartz crystal microbalance (12) are available on axis, as well as off-axis QMS (13). The TOFMS is equipped with an electron gun for electron impact ionization (not shown) but also enables photo-ionization using an external laser.…”