On the Shape of C ₆ H ₆ ⁺

Abstract

equipped with a pulsed molecular bean1 source and a threshold photoelectron spectrometer that used standard ZEKE pulsedfield ionization (ZEKE-PFI) electron optics.Within the delayed-field-ionizatio~l and electron-collection veeion of the saectrom-

Jahn-Teller Spectral Fingerprint in Molecular Photoemission:C60

“…When only H (1) g is included, all satellite structures above 200 meV are absent, and do not reappear even if we arbitrarily increase the H (1) g coupling to larger and larger values. This rules out the possibility to attribute the 230 meV structure to an "electronic" splitting [5].…”

“…1). The result is a much narrower spectrum (H (1) g is now omitted), showing a highenergy satellite at a significantly (10%) higher energy than ω Hg 8 . This increase in vibronic excitation energy above the purely vibrational ω for the v=1-phonon excitation of a trivial displaced oscillator is in fact a characteristic signature of the dynamic JT effect, and can be understood on the basis of symmetry.…”

“…Photoemission (PE) from a closed-shell high-symmetry molecule, involving Jahn-Teller (JT) effect in the final state, is accompanied by characteristic vibronic structures in the measured hole spectrum [1]. Although accurate spectral calculations have recently appeared in the chemical literature, e.g.…”

“…When we include H (1) g alone we find (inset) that the thermally broadened asymmetric main peak is well reproduced. Therefore H (1) g is the main responsible for the large broadening.…”

“…2: Vibronic excitation energies for a single Hg mode coupled to the hu level, as a function of coupling, for a ratio g (2) /g (1) characteristic of the H (7/8) g modes. The average refers to the multiplet originating from the 1-phonon states.…”