Theory

The main research direction of our group at the theory side are ab initio quantum scattering calculations. We are primarily interested in studying collisional processes for simple diatomic molecules, which can be described in a fully quantum way starting from the first principles. The model example is molecular hydrogen colliding with noble gas atoms [7, 19, 22, 26] and with itself [69, 71]. On the one hand, these studies are motivated by testing the quantum-chemical calculations [7, 19] and studying collisional physics at molecular level [2, 5, 7, 37]. On the other hand, motivation is astrophysical [67, 69] and atmospheric [48, 54, 61, 66] applications. Depending on the context, the collision energy in our calculations spans from ultracold regime [68], where the single partial wave dominates the collision physics, through the intermediate range that is relevant to many astrophysical applications [67, 69, up to high temperature (room temperature and higher), where over hundred partial waves have to be included [48]. Our quantum scattering calculations are strongly related to the problem of molecular spectra simulations, where often the collision-induced line-shape effects play an important role [69]. Another example of our activity on the theory side are calculations of molecular structure and their properties, which are mostly related to supporting our experimental projects. One example is calculations of the hyperfine structure in molecular hydrogen [36, 45] and its isotopologues [33, 35, 46, 47], and more general considerations related to generic properties related to hyperfine interactions [56, 64]. Another example is developing a new approach to looking for magic wavelengths in molecules and identifying a series of magic wavelengths in H2 [57]. Our other projects span from calculating molecular properties based on well-established methodologies such as calculating line intensities of molecular transitions [70] up to more exotic considerations such as studying possibility of enhancing the sensitivity of optical cavity to variations in the fine-structure constant [50].