@article{32f225a56f5b408f97160852d09867c0,

title = "Temperature dependence of the rotational life times in solid H2",

abstract = "We have studied the temperature dependence of the nuclear transverse and longitudinal relaxation times in solid H2 for ortho concentrations 10-3 < X < 10-2 between 0.4 K and the triple point, 13.9 K. We find a striking temperature dependence in T2 over the whole temperature range. This new effect is ascribed to a coupling between molecular rotation and lattice vibrations, which is brought into evidence by the narrow width of the spectral density of the rotational fluctuations at low X.",

author = "Buzerak, {R. F.} and M. Chan and H. Meyer",

note = "Funding Information: SOLID ORTHO and para H2 mixtures present a number of analogies to a dilute antiferromagnet. 1 It is well known that in the solid state, the ortho molecules have a rotational angular momentum J = 1, an electric quadrupole moment eQ and the nuclear spins are parallel with a total spin I = 1. They correspond to a magnetic ion. Para-molecules are spherically symmetric with zero angular momentum and spin, and give no NMR signal. Neighboring J = 1 molecules are coupled via electric quadrupole-quadrupole interaction, which is the dominant anisotropic interaction under conditions of saturated vapor pressure. The characteristic parameter of this interaction is then Fo = 6e2Q2/25RS where R is the distance between nearest neighbors and with an effective value F\[ks = 0.82 K. x Nuclear relaxation times offer a means to study the spectral densities of the rotational fluctuations as a function of the dilution of the J = 1 species, and recently there has been progress in the calculation of the shape of.these spectral densities over a large range of the molefraction X of the J = 1 molecules. 2-5 In this paper we describe the results for X < 10 -2 of a systematic study of the nuclear longitudinal and transverse relaxation times over the range 10-3< X < 2 x 10 -1. These measurements, at the frequencies 6o/21r of 5.3 and 29 MHz, were carried out over the temperature range 0.4 ~< T <~ 13.7 K, the upper temperature being close to the triple point. Our data are in fact an extension of the work by Hardy and Gaines 6 who carried out such measurements at 4.2 K. Our most striking result is a strong temperature dependence of T2 which is unrelated to the classical diffusional line-narrowing. This new effect is especially noticeable for X < 0.01 where the linewidth is determined primarily by * Research supported by a grant from the Army Re-search Office Durham and from the Office of Naval Research.",

year = "1976",

doi = "10.1016/0038-1098(76)91760-9",

language = "English (US)",

volume = "18",

pages = "685--687",

journal = "Solid State Communications",

issn = "0038-1098",

publisher = "Elsevier Limited",

number = "6",

}