Experimental studies of fast fragments of H Rydberg matter

A comprehensive pulsed-laser time-of-flight (TOF) study of H Rydberg matter (RM) fragments is presented. The nature of the fragments released with well-defined kinetic energies of 9-24 eV is investigated: the detected fragments are found to be H* in Rydberg states with principal quantum number n > 28. The only way to produce such states is from Coulomb explosions in a pre-formed easily laser-fragmented molecular entity. Non-symmetric angular distributions of the fragments are measured and Coulombic shockwave phenomena are observed, which prove that the phase of origin is not a gas but an RM phase. The fast particles are concluded to be formed in two-, three- and four-particle Coulomb explosion processes in an H RM cluster. Laser intensity variation measurements indicate that between four and six photons with a total energy of 8.8-13 eV take part in the RM fragmentation. This proves that laser-induced processes in H-2 or H-2(+) molecules, even in the RM phase, are excluded for energetic reasons. A feasible H RM formation mechanism is deduced from the signal variation with H-2 pressure, with the dissociation of H-2 on the emitter surface as the rate limiting step. The principal quantum number of H Rydberg species H* reaching the detector is estimated to be n > 32 from a comparison of the calculated ionization rate of the H* species in the electric field inside the detector with measurements.