The ortho-to-para conversion in solid hydrogen, catalyzed by hydrogen atoms

Infrared studies of ortho-para conversion at Cl-atom and H-atom impurity centers in cryogenic solid hydrogen

“…The measurements presented here compliment previous ESR measurements [10][11][12][13][14][15] of H-atom diffusion in solid hydrogen because the kinetics of o/p conversion depends on the H-atom diffusion rate. These FTIR measurements are also comparable to older gas-chromatography measurements [11] which measured X o in hydrogen solids before and after exposure to H-atoms, but in this case, we can follow the o/p conversion kinetics directly and nondestructively.…”

“…Since the H-atom is also paramagnetic, it too can serve as an o/p catalyst within the solid. In addition, even at the low temperatures at which these experiments were conducted (1.93 K), the H-atom can still diffuse via quantum mechanical tunneling [10][11][12][13][14][15]. Thus, if the H-atom quantum diffusion rate is large, one H-atom can convert large numbers of oH 2 molecules over long distances.…”

“…The o/p conversion kinetics in solid hydrogen catalyzed by the H-atom product, however, should be qualitatively different because the H-atom is mobile even at temperatures below 2 K. It is well known that H-atoms diffuse in solid hydrogen by quantum mechanical tunneling at temperatures below 4 K [10][11][12][13][14][15]. The most recent ESR measurements from the group at Nagoya University indicate the H-atoms translate via «chemical diffusion» whereby the H-atom moves by the H + H 2 → H 2 + H chemical reaction between an H-atom and one of its surrounding H 2 molecules in the solid [14].…”

EPR Study of H and D Atoms in Quench-Condensed Solid D $$_{2}$$ 2

“…Some studies with the use of EPR spectroscopy [1][2][3] provide a circumstantial evidence that a good part of H, D, and T atoms trap at the imperfections of the crystal lattices of solid molecular hydrogens, H 2 , D 2 , T 2 , which may govern the quantum diffusion rate [2] and estimation of the energy stored in the matrix. We here report on our EPR investigation of H and D atoms in the matrix of solid molecular deuterium which shows, along with known centers, new EPR spectra of H and D that cannot be related to atoms being localized at the regular sites of the perfect crystal lattice.…”

“…Investigation of impurities in solid molecular hydrogens has attracted continuous attention, which is due to both the manifestation of quantum effects in these systems (e.g., 1.9 0.28 (7) β-Irradiation [1] 1.8 -β-Irradiation [9] 1.5 −0.28 (2) Deposition [12] quantum diffusion of impurity particles, ortho-para conversion of matrix molecules, isotope exchange reactions) and the quest for better cryogenic fuel. Some studies with the use of EPR spectroscopy [1][2][3] provide a circumstantial evidence that a good part of H, D, and T atoms trap at the imperfections of the crystal lattices of solid molecular hydrogens, H 2 , D 2 , T 2 , which may govern the quantum diffusion rate [2] and estimation of the energy stored in the matrix.…”