Photoelectron Spectroscopy of Coronene Molecules Embedded in Helium Nanodroplets

We present the first measurement of a one-photon extreme-ultraviolet photoelectron spectrum (PES) of molecules embedded in superfluid helium nanodroplets. The PES of coronene is compared to the gas and solid-phase PESs, and to electron spectra of embedded coronene generated by charge transfer and Penning ionization through ionized or excited helium. The resemblance of the He-droplet PES to the one of the solid phase indicates that mostly coronene clusters are photoionized. In contrast, the He-droplet Penning-ionization electron spectrum is nearly structureless, indicating strong perturbation of the ionization process by the He droplet. These results pave the way to extreme ultraviolet photoelectron spectroscopy (UPS) of clusters and molecular complexes embedded in helium nanodroplets.