Characterizing BH Bound and Resonant States for Plasma Edge Applications

The International Thermonuclear Experimental Reactor (ITER) is presently being designed to be a full tungsten machine with boronized walls. A consequence of boronization is the formation of boron hydrides at the plasma edge. With this in view, we have made detailed calculations of the Rydberg and resonant states of the BH molecule, neither of which has been well-studied. In particular, the neutral resonant states are known to be pathways for many dissociative processes that can release boron and are therefore of great importance. A good-quality BH+ target wave function was first obtained using a complete active space configuration interaction model. Subsequently, the R-matrix method was used to calculate the bound and resonant states of the neutral BH molecule across a moderately dense grid of 81 internuclear distances. We have identified many Rydberg states and characterized them by using their quantum defects. Several resonant states, which are likely to be important for processes like dissociative recombination, have also been identified, and their resonant widths have been obtained. The molecular states, together with the corresponding resonance widths, would be very important for initiating further collisional studies such as dissociative recombination, dissociative excitation, resonant vibrational excitation, and deexcitation and will prove useful for edge plasma applications.