Spectroscopic Observation of Atomic Hydrogen Radicals Entrapped in Icy Hydrogen Hydrate

摘要

At sufficiently low temperatures, a single hydrogen atom (H atom) that becomes an atomic free radical by irradiation is known to be a relatively stable paramagnetic species in a wide variety of substances. Solid hydrogen in particular is a well-known quantum medium that has attracted much attention for its potential incorporation in novel materials having high-temperature superconductivity, because of its structural, magnetic, and electronic properties. These molecular properties of H atoms at ultralow temperature have been explored through the identification of unpaired electrons in H atoms observed by electron spin resonance (ESR) spectroscopy. Pure solid para-hydrogen has been used only as a valuable matrix material and enables high-resolution measurements via ESR spectroscopy due to its paired nuclear spins.