Coulomb explosion imaging and the CH2+ molecule

Coulomb-explosion imaging ofCH2+: Target-polarization effects and bond-angle distribution

“…Bearing in mind the various approximations made in the treatment of the target effects and the description of the Coulomb explosion process, the amount of agreement between experimental and simulated V-space data obtained suggests that the geometry of the CH 2 + molecular ion is well described by the calculated R-space structure [17] used as input for the simulation algorithm. The agreement is certainly better than the one reached in Refs.…”

“…2, 4, and 5, while the second one (dashed lines) is referred to as static simulation. The molecular geometry input of the simulation is based on the work of Osmann et al [17], with an equilibrium bond angle of ␣ R = 140.5°and an internuclear C-H distance of r i = 1.096 Å. Figure 2 shows the effect of the polarization force on the measured orientation of the molecule.…”

“…[15]) performed in our laboratory, a small but conspicuous disagreement was found between the experimentally determined bond-angle distribution and theoretical calculations [16]. Several efforts have been made to search for the origin of this disagreement including extended calculations [17] to investigate the precision of the theoretical approach. Here, we report on a highstatistics CEI experiment and its analysis, which includes an improved treatment of the various target effects.…”

A Theoretical Study of ã4A2 CH2+

“…Earlier images (10) were interpreted as leading to a bending probability distribution with a maximum at a structure that was significantly more bent than theory calculated. One explanation of the results obtained in (10) was that excited doublet electronic states were contributing to the image, but this possibility could be discounted (4). However, for the isoelectronic diatomic molecules NH + and CH the first excited quartet states are low, having T e values of 500 and 5844 cm −1 respectively (11), and so just possibly the first excited quartet state of CH + 2 might have been contributing to the image.…”

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The potential energy surface and dipole moment surfaces of theã 4 A 2 electronic state of CH + 2 are calculated ab initio using an augmented correlation-consistent polarized valence quadruple-ζ (aug-cc-pVQZ) basis set, with the incorporation of dynamical correlation using the coupled cluster method with single and double excitations and perturbatively connected triple excitations [CCSD(T)]. We use these surfaces in the MORBID program system to calculate rotation and rotation-vibration term values for a-state CH + 2 , CD + 2 , and CHD + and to simulate the rotation and rotation-vibration absorption spectrum of CH + 2 in theã 4 A 2 electronic state.

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