Vibrationally Resolved Inner‐Shell Photoexcitation of the Molecular Anion C₂⁻

Abstract

Carbon 1s core-hole excitation of the molecular anion C 2 À has been experimentally studied at high resolution by employing the photon-ion merged-beams technique at a synchrotron light source. The experimental cross section for photo-doubledetachment shows a pronounced vibrational structure associated with 1s u ! 3s g and 1s g ! 1p u core excitations of the C 2 À ground level and first excited level, respectively. A detailed Franck-Condon analysis reveals a strong contraction of the C 2 À molecular anion by 0.2 Å upon this core photoexcitation. The associated change of the molecule's moment of inertia leads to a noticeable rotational broadening of the observed vibrational spectral features. This broadening is accounted for in the present analysis which provides the spectroscopic parameters of the C 2 À 1s À 1 u 3s 2 g 2 S þ u and 1s À 1 g 3s 2 g 2 S þ g core-excited levels.

Isomer-specific photofragmentation of C3H3+ at the carbon K-edge

“…26–28 Using this technique the electronic structure of the unoccupied states can be studied. 29–32 Moreover, it allows one to measure fast dynamic dissociation processes, which take place on a time scale of a few femtoseconds. 31…”

“…[26][27][28] Using this technique the electronic structure of the unoccupied states can be studied. [29][30][31][32] Moreover, it allows one to measure fast dynamic dissociation processes, which take place on a time scale of a few femtoseconds. 31 In this paper, we present the X-ray absorption spectra of a mixture of three different C 3 H 3 + isomers at the C 1s edge by measuring the ion yield of selected photofragmentation channels using the merged-beams technique.…”

Correlating Stokes Shift with Huang‐Rhys Parameter for Diatomic Molecules: Effects of Finite Temperature, Anharmonicity and Breakdown of Franck‐Condon Approximation

“…Although the RSES systems are ubiquitous since internuclear distance increases upon photoexcitation in the excited state, examples of a few LSES systems are known where the bond length shrinks following absorption of high-energy photons. [26][27][28] In this regard, to consider both the RSES and LSES cases simultaneously, it is quite natural to introduce the Huang-Rhys (HR) parameter, which explained the shape of absorption and emission bands for electronic transitions on F-centers, to which Huang and Rhys majorly contributed. [29] The HR parameter correlates the coupling of the electronic states to the nuclear coordinates, defined in the context of a displaced harmonic oscillator model with similar curvature for both the ground and excited PESs.…”

“…This ‘mirror image’ relationship is independent of the position of the excited‐state PES, whether it is right‐shifted or left‐shifted to the ground‐state PES, [25] written as the right‐shifted excited surface (RSES) system and the left‐shifted excited surface (LSES) system. Although the RSES systems are ubiquitous since internuclear distance increases upon photoexcitation in the excited state, examples of a few LSES systems are known where the bond length shrinks following absorption of high‐energy photons [26–28] . In this regard, to consider both the RSES and LSES cases simultaneously, it is quite natural to introduce the Huang‐Rhys (HR) parameter, which explained the shape of absorption and emission bands for electronic transitions on F‐centers, to which Huang and Rhys majorly contributed [29] .…”