Advances in experimental methodology aligned with technological developments, such as 3rd generation light sources, X-ray Free Electron Lasers, and High Harmonic Generation, have led to a paradigm shift in the capability of X-ray spectroscopy to deliver high temporal and spectral resolution on an extremely broad range of samples in a wide array of different environments. Importantly, the complex nature and high information content of this class of techniques mean that detailed theoretical studies are often essential to provide a firm link between the spectroscopic observables and the underlying molecular structure and dynamics. In this paper, we present approaches for simulating dynamical processes in X-ray spectroscopy based upon on-the-fly quantum dynamics with a Gaussian basis set. We show that it is possible to provide a fully quantum description of X-ray spectra without the need of precomputing highly multidimensional potential energy surfaces. It is applied to study two different dynamical situations, namely, the core-hole lifetime dynamics of the water monomer and the dissociation of CF + 4 recently studied using pump-probe X-ray spectroscopy. Our results compare favourably to previous experiments, while reducing the computational effort, providing the scope to apply them to larger systems. https://doi.

Successful chromatographic use of a chemically reactive solid, silver nitrate, has been demonstrated using very small samples of unsaturated hydrocarbons. Although such a column has to be operated at relatively higher temperatures to make the unsaturates mobile, its use should simplify many analyses because saturates are not retained.

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Conventional systems for the measurement of magnetic circular dichroism (MCD) employ a dc magnet in the sample space of a circular dichroism spectropolarimeter, where the state of polarization of the light beam is modulated between left and right circular. The photometric system of the instrument measures the difference between sample absorbances for the two states of polarization of the light beam. The method described in this paper uses a fixed state of polarization of the light beam, left or right circular, an alternating or pulsed magnetic field, and otherwise the same photometric system as the conventional method. The two methods are shown to be mathematically and physically equivalent. The proposed method offers two fundamental advantages: (1) Only the magnetically induced circular dichroism is measured, even in the presence of natural optical activity, and (2) the method is capable of extension to spectral regions where polarization modulation is difficult to achieve. Experimental apparatus using the two methods are described and their relative merits are discussed.