Vibrational cooling in a cold ion trap:Vibrationally resolved photoelectron spectroscopy of cold C_(60)~-anions

摘要

We demonstrate vibrational cooling of anions via collisions with a background gas in an ion trap attached to a cryogenically controlled cold head(10-400 K).Photoelectron spectra of vibrationally cold C_(60)~-anions,produced by electrospray ionization and cooled in the cold ion trap,have been obtained.Relative to spectra taken at room temperature,vibrational hot bands are completely eliminated,yielding well-resolved vibrational structures and a more accurate electron affinity for neutral C_(60).The electron affinity of C_(60)is measured to be 2.683 + 0.008 eV.The cold spectra reveal complicated vibrational structures for the transition to the C_(60)ground state due to the Jahn-Teller effect in the ground state of C_(60)~-.Vibrational excitations in the two A_g modes and eight H_g modes are observed,providing ideal data to assess the vibronic couplings in C_(60)~-.