A method for calculating the generalized oscillator strengths (GOSs) and differential cross section (DCS) with vibration and rotation resolution is presented. The importance of accounting for the rotational contribution is to be emphasized since it has not previously been considered in GOS calculations. Although largely neglected due to its small effect on various properties, the rotational resolution proved to be fundamental in the study of certain phenomena, such as the interference between rotational states in a molecule. As the general goal of this work is to obtain theoretical values comparable to high resolution experiments, special care was taken on the calculation of the electronic part of the scattering amplitude, particularly in what concerns the choice of the atomic basis set. Accordingly, even-tempered basis sets have proved to lead to good results. The helium atom was taken as a model system for this aspect of the problem. Then, GOS and DCS, for explicit vibrational and rotational transitions, were calculated for hydrogen and nitrogen molecules. For higher accuracy, a non-Franck–Condon approach was used to obtain transitions involving vibrational states. The resultant values have shown good agreement with the available experimental data.
We show that two-particle interferences can be used to probe the nuclear motion in a doublyexcited hydrogen molecule. The dissociation of molecular hydrogen by electron impact involves several decay channels, associated to different molecular rotational states, which produce quantum interferences in the detection of the atomic fragments. Thanks to the correlations between the angular momentum and vibrational states of the molecule, the fragments arising from each dissociation channel carry out a phase-shift which is a signature of the molecule rotation. These phase-shifts, which cannot be observed in a single-atom detection scheme, may be witnessed in realistic experimental conditions in a time-of-flight coincidence measurement. We analyse the interferences arising from the two lowest-energy rotational states of a para-hydrogen molecule. Our result shows the relevance of two-fragments correlations to track the molecular rotation.
We discuss the use of a region of uniform and constant magnetic field in order to implement a two-state atomic polarizer for an H(2S) beam. We have observed that a device with such field configuration is capable of achieving an efficient polarization for a wide range of magnetic field intensities and atomic velocities. In addition, we establish a criterion that must be met to confirm a successful polarization. That is possible due to a specific beating pattern for the Lyman-α radiation expected for the outgoing two-state atomic beam.
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