Theory of polarization-averaged core-level molecular-frame photoelectron angular distributions: III. new formula for p- and s-wave interference analogous to Young's double-slit experiment for core-level photoemission from hetero-diatomic molecules

We present a new variation of Young's double-slit formula for polarization-averaged molecular-frame photoelectron angular distributions (PA-MFPADs) of hetero-diatomic molecules, which may be used to extract the bond length. So far, empirical analysis of the PA-MFPADs has often been carried out employing Young's formula in which each of the two atomic centers emits a s-photoelectron wave. The PA-MFPADs, on the other hand, can consist of an interference between the p-wave from the X-ray absorbing atom emitted along the molecular axis and the s-wave scattered by neighboring atom, within the framework of Multiple Scattering theory. The difference of this p-s wave interference from the commonly used s-s wave interference causes a dramatic change in the interference pattern, especially near the angles perpendicular to the molecular axis. This change involves an additional fringe, urging us to caution when using the conventional Young's formula for retrieving the bond length. We have derived a new formula analogous to Young's formula but for the p-s wave interference. The bond lengths retrieved from the PA-MFPADs via the new formula reproduce the original C-O bond lengths used in the reference ab-initio PA-MFPADs within the relative error of 5 %. In the high energy regime, this new formula for p-s wave interference converges to the ordinary Young’s formula for the s-s wave interference. We expect it to be used to retrieve the bond length for time-resolved PA-MFPADs instead of the conventional Young's formula.

Measuring the photoelectron emission delay in the molecular frame

How long does it take to emit an electron from an atom? This question has intrigued scientists for decades. As such emission times are in the attosecond regime, the advent of attosecond metrology using ultrashort and intense lasers has re-triggered strong interest on the topic from an experimental standpoint. Here, we present an approach to measure such emission delays, which does not require attosecond light pulses, and works without the presence of superimposed infrared laser fields. We instead extract the emission delay from the interference pattern generated as the emitted photoelectron is diffracted by the parent ion’s potential. Targeting core electrons in CO, we measured a 2d map of photoelectron emission delays in the molecular frame over a wide range of electron energies. The emission times depend drastically on the photoelectrons’ emission directions in the molecular frame and exhibit characteristic changes along the shape resonance of the molecule.

Probing the molecular frame of uracil and thymine with high-harmonic generation spectroscopy

We present here HHG spectra of uracil and thymine, computed by a real-time formulation of configuration interaction with single excitations. Spectra are obtained as three-dimensional and molecular-plane averages, and as single-polarisation responses.

Molecular Frame Dipole Moment of Diatomic Molecules within Relativistic Coupled-Cluster Framework: A Comparative Study of Expectation Value vs. Energy Derivative Approach

The ground state molecular frame permanent dipole moment of alkaline earth metal monofluorides and the group-IIB monohydrides have been calculated using two analytic methods: Z-vector method and the linear expectation value method. Results obtained from this methods have been compared with the experimental values and different contributing terms to the total permanent dipole moment have been discussed thoroughly.<br>

Molecular Frame Dipole Moment of Diatomic Molecules within Relativistic Coupled-Cluster Framework: A Comparative Study of Expectation Value vs. Energy Derivative Approach

The ground state molecular frame permanent dipole moment of alkaline earth metal monofluorides and the group-IIB monohydrides have been calculated using two analytic methods: Z-vector method and the linear expectation value method. Results obtained from this methods have been compared with the experimental values and different contributing terms to the total permanent dipole moment have been discussed thoroughly.<br>