Single and double ionization of the camphor molecule excited around the C 1s edge

Abstract

Our PEPIPICO spectrum clearly demonstrated the formation of doubly ionic dissociative species. From a slope analysis, we propose a secondary decay after a deferred charge separation mechanism in which, after a few steps, the camphor dication dissociates into C2 H3 (+) and C3 H5 (+) . This is the main relaxation route observed at 270 eV and 330 eV. The large energy difference between the mono and the dication (of the order of 258.2 kcal/mol) may explain the experimentally observed absence of stable dications in the spectra, because their formation is disadvantaged energetically.

Fragmentation dynamics of doubly charged camphor molecule following C 1s Auger decay

“…58,62 This is expected for C 1s edge photoionisation as the molecule can undergo double and triple ionisation by highly efficient secondary mechanisms like Auger decay, 3 leading to higher fragmentation as observed previously. 42 This is further confirmed by the presence of the observed fragments in photoelectron-photoion-photoion coincidences.…”

“…36,59 In a previous PEPIPICO fragmentation study of camphor, photon energies of 270 eV and 330 eV were used for ionisation. 42 To gain a deeper understanding of the fragmentation dynamics of the molecule, we implemented the VMI-PEPIPICO technique at 292.4 eV (having the highest ion yield) for ion-VMI and 304.9 eV for electron-VMI (e-VMI) (where the VMI resolution (DE/E) is better at around 7%, as compared to low energy electrons produced by photons of energy 292.4 eV).…”

“…The convergence threshold of the density matrix is kept at 10 À6 during the optimisation. We matched it with the known geometry of the neutral (1S)-(À)-Camphor from earlier studies 42,57,58 to validate our geometry optimisation. Usually, the MD simulation is performed with an NVT (moles, volume, and temperature) ensemble and the velocity Verlet algorithm is used for time integration.…”

“…[35][36][37][38] Moreover, dichroism is observed in the photoion emission of other chiral and achiral molecule. [39][40][41] Though the first study 42 on the fragmentation of camphor following photoexcitation at the carbon K-edge was using the electronion-ion coincidence technique, [43][44][45] some questions, such as how does a dicationic molecule dissociate in kinematically complete scheme? were left unanswered, and hence motivating this study.…”

Detecting handedness of spatially oriented molecules by Coulomb explosion imaging

“…Their flight directions can be observed experimentally as momentum distributions of the CH + 3 ions resulting from multiple ionization followed by Coulomb explosion of the molecule. 15,16 We assume that two-body dissociation events produce equal initial momenta for CH + 3 fragments at three different molecular sites. By normalizing the size of the Newton sphere to one, the momenta distributions are given by the position distributions of the CH 3 groups.…”