Experimental observation of relativistic effects on electronic wavefunction for iodine lone-pair orbital of CF3I

Electron Momentum Spectroscopy Study on the Valence Electronic Structure of Dimethyl Sulfide Considering Vibrational Effects

We report an electron momentum spectroscopy study on the valence electronic structure of dimethyl sulfide. The binding energy and electron momentum profiles are measured using a high-sensitivity (e, 2e) apparatus employing a symmetric non-coplanar geometry at an incident energy of 1200 eV plus binding energy. The measurements are compared with the theoretical calculations by density functional theory performed both at equilibrium molecular geometry and by considering vibrational effects through a harmonic analytical quantum mechanical approach. The results demonstrate a significant influence of nuclear vibrational motions on the momentum profiles for valence orbitals of dimethyl sulfide, especially for 5b₂, 1a₂, and 4b₂. A detailed analysis shows that the observed vibrational effects come mainly from vibrational normal modes breaking the mirror symmetry of (CH₃)₂S with respect to a plane perpendicular to the O-S-O plane.

Development of an electron momentum spectrometer for time-resolved experiments employing nanosecond pulsed electron beam

The low count rate of (e, 2e) electron momentum spectroscopy (EMS) has long been a major limitation of its application to the investigation of molecular dynamics. Here we report a new EMS apparatus developed for time-resolved experiments in the nanosecond time scale, in which a double toroidal energy analyzer is utilized to improve the sensitivity of the spectrometer and a nanosecond pulsed electron gun with a repetition rate of 10 kHz is used to obtain an average beam current up to nA. Meanwhile, a picosecond ultraviolet laser with a repetition rate of 5 kHz is introduced to pump the sample target. The time zero is determined by photoionizing the target using a pump laser and monitoring the change of the electron beam current with time delay between the laser pulse and electron pulse, which is influenced by the plasma induced by the photoionization. The performance of the spectrometer is demonstrated by the EMS measurement on argon using a pulsed electron beam, illustrating the potential abilities of the apparatus for investigating the molecular dynamics in excited states when employing the pump-probe scheme.

Vibrational Effects on Electron Momentum Distributions of Outer-Valence Orbitals of Oxetane

Vibrational effects on electron momentum distributions (EMDs) of outer-valence orbitals of oxetane are computed with a comprehensive consideration of all vibrational modes. It is found that vibrational motions influence EMDs of all outer-valence orbitals noticeably. The agreement between theoretical and experimental momentum profiles of the first five orbitals is greatly improved when including molecular vibrations in the calculation. In particular, the large turn-up at low momentum in the experimental momentum profile of the 3b1 orbital is well interpreted by vibrational effects, indicating that, besides the low-frequency ring-puckering mode, C-H stretching motion also plays a significant role in affecting EMDs of outer-valence orbitals of oxetane. The case of oxetane exhibits the significance of checking vibrational effects when performing electron momentum spectroscopy measurements.

Observation of the interference effect in vibrationally resolved electron momentum spectroscopy of H2

We report the first measurement on vibrationally resolved electron momentum spectroscopy of H2 by using a high-resolution (e, 2e) spectrometer. The vibrational-specific experimental momentum profiles have been obtained and shown to be in agreement with calculations of (e, 2e) ionization cross sections taking into account the vibrational wave functions. Distinct deviations from Franck-Condon predictions have been observed in vibrational ratios of cross sections, which can readily be ascribed to the Young-type two-center interference. Unlike previous (e, 2e) work, the present observation of an interference effect does not rely on the comparison with the one-center atomic cross section.

Quasi-classical trajectory calculation of the chemical reaction Sr + CF3I

In this paper, the dynamical properties of the product SrI, which is formed in the reaction Sr + CF3I, were studied by means of the quasi-classical trajectory method based on the extended London–Eyring–Polanyi–Sato potential energy surface. The vibrational distribution, rotational distribution, reaction cross section, and rotational alignment of the product SrI were calculated, and the mechanism of the title reaction has also been discussed. The calculated vibrational and rotational distributions show that their peak values are located at v = 23 and J = 110 at a collision energy of Ecol = 0.83 eV. These results are in good agreement with the results in Stolte’s experiment. And the results obtained in this paper also indicate that the reaction cross section increases with increasing collision energy (from 0.5 to 1.5 eV), whereas the product rotational alignment decreases.