Slow photoelectron velocity-map imaging of cold C7− and C9−

Abstract

High-resolution anion photoelectron spectra of cryogenically cooled C 7 − and C 9 − clusters obtained using slow photoelectron velocity-map imaging are presented, providing insight into the vibronic structure of neutral C 7 and C 9. These spectra yield accurate measurements of vibrational frequencies for the neutral clusters as well as electron affinities of 3.3517(4) and 3.6766(14) eV for C 7 and C 9 , respectively. In the C 7 − spectrum, transitions involving the previously unreported v 1 and v 2 symmetric stretching modes, as well as the v 9 , v 10 , and v 11 asymmetric bending modes, are assigned. Spin-orbit splitting is observed for several transitions in this spectrum, giving an energy difference of 28(6) cm −1 between the 2 Π 1/2g and 2 Π 3/2g spin-orbit levels of the C 7 − anion. In the spectrum of C 9 − , transitions involving the previously unreported symmetric stretch v 1 and the asymmetric bend v 11 are observed. In both spectra, several features are assigned to Franck-Condon forbidden transitions involving the doubly degenerate v 10 and v 11 modes of C 7 and the v 13 and v 14 modes of C 9. The appearance of these transitions is attributed to Herzberg-Teller coupling between the electronic states of the neutral clusters. Additional FC-forbidden transitions to states previously observed in gasphase infrared experiments are observed and attributed to vibronic coupling between the electronic states of the anion, resulting in non-totally symmetric character in the anion's full vibrational ground state. Finally, consideration of the energy dependence of detachment cross sections and Dyson orbital analyses reveal that addition of more carbon atoms to the linear chain results in photodetachment from delocalized molecular orbitals with increasing nodal structure, leading to threshold photodetachment cross sections that differ considerably from simple symmetry considerations.

High-Resolution Photoelectron Spectroscopy of Cryogenically Cooled NO3̅

“…(2) are intimately connected to the PADs of different detachment transitions, and differences in threshold behavior tend to occur together with different PADs. 49,51 This is true in NO3, where the PAD for A is consistent with p-wave detachment, while B displays the expected trend for a transition comprising of s-and d-wave detachment. The disparity in the PADs of A and B, coupled with their threshold behavior, unequivocally shows that B gains its intensity through pJT-coupling.…”

Radiative cooling of carbon cluster anions C2n+1− (n = 3–5)

“…where ρ 0 is the density of states of the neutral cluster and Φ is the adiabatic detachment energy, taken from photoelectron spectroscopy measurements [43,44]. The pre-exponential factor ω is proportional to the electron capture cross section [42] and is here approximated as a constant equal to 10 14 s −1 [20].…”

“…Ions with Table 1. Fit parameters P and τ for spontaneous neutralization yield, values of τ ≈ ktot(Φ) −1 from our SHC model, and adiabatic detachment energies (Φ) from literature [43,44]. Statistical uncertainties in the last digit are given in parentheses.…”

“…For the C − 7 spectrum, the spectrum was constructed using by integrating a storage time of 10 s for each photon energy (wavelength). In each panel in Figure 4, the adiabatic detachment energy (Φ) determined from photo-electron spectroscopy [43,44] is indicated by a vertical dashed line. For C − 9 and C − 11 , the vertical bars indicate the energies of electronically excited states of the anion, measured by Forney et al in a neon matrix [50].…”

“…The heavy solid lines are 10-point moving averages. Vertical dashed lines show the adiabatic detachment energies reported from photo-electron spectroscopy[43,44]. Vertical bars show energies of electronic transitions of C − 9 and C − 11 from matrix isolation spectroscopy[50].…”