Electronic spectroscopy of He@C+60 for astrochemical consideration

The electronic spectrum of the endohedral fullerene He@C+60 observed by messenger spectroscopy in a cryogenic ion trap is presented. The role played by the messenger tag in the adopted experimental method is evaluated by recording spectra of He@C+60-Hen with n=1 4. The results indicate a linear shift of 0.7A in the wavelengths allowing accurate gas phase values to be reported. The presence of the helium inside the cage shifts the absorption bands by 2 3 Atoward shorter wavelengths compared to C+60. The magnitude of this displacement will enable searches for the spectral signatures of this fullerene analogue in interstellar environments by absorption spectroscopy. The implications for potential astronomical detection are scussed.