Double-slit experiment with a polyatomic molecule: vibrationally resolved C 1s photoelectron spectra of acetylene

Abstract

We report the first evidence for double-slit interferences in a polyatomic molecule, which we have observed in the experimental carbon 1s photoelectron spectra of acetylene (or ethyne). The spectra have been measured over the photon energy range of 310-930 eV and show prominent oscillations in the intensity ratios σ g (υ)/σ u (υ) for the vibrational quantum numbers υ = 0, 1 and for the ratios σ s (υ = 1)/σ s (υ = 0) for the symmetry s = g, u.The experimental findings are in very good agreement with ab initio density 9

Laboratory-frame electron angular distributions: Probing the chemical environment through intramolecular electron scattering

“…The second clear peak observed in the 2a 1 and 2a ′ cross sections is located too high in energy (∼ 60 eV above threshold) to be assigned to a shape resonance, and it is interpreted to be the first unambiguous fingerprint of intramolecular scattering. Contrary to the cross section oscillations typical of the coherent emission from equivalent centers [15], the oscillatory structures of the chlorinated and methyl C 1s cross sections are not in phase opposition. In the 2a 1 and 2a ′ channels the oscillations have significantly longer periods and larger amplitudes compared to the 3a 1 and 3a ′ channels, which exhibit more regular and less damped structures.…”

Vibrational branching ratios in the photoelectron spectra of N2 and CO: interference and diffraction effects

“…In their most sophisticated version, they can even include interchannel couplings and describe some autoionization processes. They have even been used to evaluate vibrationally resolved cross section in polyatomic molecules 124,125 . In this section, we will describe the extension of these DFT-like methods to include the nuclear motion in the Born-Oppenheimer approximation.…”

Probing the role of excited states in ionization of acetylene

“…We can show that the inner plateau is due to the 3σ g → 3σ u transition rather than the 2σ u → 4σ g transition by calculating the contribution of each state to the harmonic response using Eq. (16). The contributions of the HOMO-1 and HOMO-2 to the harmonic response are also shown in Fig.…”

“…However, the cut-off energy for this inner plateau is lower than that predicted by the classical three-step model: we attribute this to suppression of ionization from the LUMO+1 due to transitions back to the HOMO-1 [66]. These transitions from the LUMO+1 to the HOMO-1 give rise to a window of enhanced harmonics (harmonics [11][12][13][14][15][16][17][18][19][20][21]. We can show that the inner plateau is due to the 3σ g → 3σ u transition rather than the 2σ u → 4σ g transition by calculating the contribution of each state to the harmonic response using Eq.…”

“…In order to overcome these shortcomings, a range of techniques, based on ab initio methods, have been developed. Pioneering ab initio studies using density functional theory (DFT) [6,15,16,31] and configuration interaction (CI) methods [32] have been used to study electron migration in molecules following sudden removal of an electron and have observed charge oscillations along the full length of the molecule with a period of several femtoseconds. The drawback of these approaches is that the initial pumping of the molecule by a laser pulse is not described.…”