Electron Spin Resonance of 87Rb Monomers on Superfluid Helium Nanodroplets and Introduction of a Simple Model for Optical Pumping

Full text: Electron spin resonance (ESR) spectroscopy on superfluid helium nanodroplets (HeN) has recently been performed for 85Rb. Electronic perturbation of the alkali-metal atom induced by the HeN leads to a droplet size dependent change of the hyperfine constant aHFS. The investigation of ESR silent species inside HeN, by measuring their interaction with an alkali-metal atom situated on the droplet surface, is expected to be more sensitive for 87Rb because of its larger hyperfine coupling (aHFS = 3417 MHz). We present new ESR spectra of single 87Rb atoms on HeN. The amplitude of ESR transitions measured by means of optically detected magnetic resonance, turned out to strongly depend on the laser polarization and power. A simple model for optical pumping on HeN has been established. Modelling of changes in the observed line shapes is expected to reveal new information concerning the droplet size dependence of aHFS and is object of current work. (author)