Long-Range Interactions for Hydrogen Atoms in Excited D States

Pressure shifts inside an atomic beam are among the more theoretically challenging effects in high-precision measurements of atomic transitions. A crucial element in their theoretical analysis is the understanding of long-range interatomic interactions inside the beam. For excited reference states, the presence of quasi-degenerate states leads to additional challenges, due to the necessity to diagonalize large matrices in the quasi-degenerate hyperfine manifolds. Here, we focus on the interactions of hydrogen atoms in reference states composed of an excited nD state (atom A), and in the metastable 2S state (atom B). We devote special attention to the cases n=3 and n=8. For n=3, the main effect is generated by quasi-degenerate virtual P states from both atoms A and B and leads to experimentally relevant second-order long-range (van-der-Waals) interactions proportional to the sixth inverse power of the interatomic distance. For n=8, in addition to virtual states with two states of P symmetry, one needs to take into account combined virtual P and F states from atoms A and B. The numerical value of the so-called C6 coefficients multiplying the interaction energy was found to grow with the principal quantum number of the reference D state; it was found to be of the order of 1011 in atomic units. The result allows for the calculation of the pressure shift inside atomic beams while driving transitions to nD states.

Atom-surface van der Waals potentials of topological insulators and semimetals from scattering measurements

The phenomenology of resonant scattering has been known since the earliest experiments upon scattering of atomic beams from surfaces and is a means of obtaining experimental information about the fundamentals...

Boriding of steel surface with beams of boron atoms

We consider a new method for hardening the steel surface, which differs from the known CHT boriding method in the possibility of creating a surface with a lower fragility. Within this approach, the boriding is carried out by treating the steel surface with atomic beams of boron at a temperature below 750 °C. In this case, a friable layer of pure boron appears on the outer surface of the steel. Then, boron atoms diffuse from this layer into the surface layers of the steel. To detect boron in a steel sample, we used the X-ray photoelectron spectroscopy method. With its help we have obtained spectra of both the outer surface of a steel sample and surface layers at depths up to 8 nm. The spectra of the surface layers showed that as a result of boriding in the sample there appeared the boron in the zero oxidation state. This fact is consistent with the notion that, in the case of a small concentration of boron, it is located on the boundaries between the grains in the surface layer of steel and strengthens the bonds between the boundaries.