Quantum crystals are characterized by zero-point-energy motions large enough to explore the details of the interaction potential beyond the harmonic approximation even at zero temperature. By making recourse to ultrahigh-resolution neutron spectroscopy, we have probed simultaneously three observables sensitive to anharmonic effects in solid para-H-2 over a wide temperature range, namely, Bragg scattering, molecular root-mean-square displacements, and the spectral linewidth of the J = 0 -> 1 rotational transition which, on average, amounts to a half-width at half-maximum of 1.8 +/- 0.2 mu eV. These three quantities show no measurable variation with temperature, thus signaling the existence of a fully expanded crystal across the entire solid phase. Our results provide unambiguous experimental evidence for the intrinsic quantum character of this fundamental molecular solid.
Solid para-hydrogen as the paradigmatic quantum crystal: Three observables probed by ultrahigh-resolution neutron spectroscopy
Mondelli Claudia;
2012
Abstract
Quantum crystals are characterized by zero-point-energy motions large enough to explore the details of the interaction potential beyond the harmonic approximation even at zero temperature. By making recourse to ultrahigh-resolution neutron spectroscopy, we have probed simultaneously three observables sensitive to anharmonic effects in solid para-H-2 over a wide temperature range, namely, Bragg scattering, molecular root-mean-square displacements, and the spectral linewidth of the J = 0 -> 1 rotational transition which, on average, amounts to a half-width at half-maximum of 1.8 +/- 0.2 mu eV. These three quantities show no measurable variation with temperature, thus signaling the existence of a fully expanded crystal across the entire solid phase. Our results provide unambiguous experimental evidence for the intrinsic quantum character of this fundamental molecular solid.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
