Nuclear Magnetic Resonance of the Solid Phases of HCl, HBr, and HI

Abstract

Proton relaxation times, second moments, and deuteron line splittings have been measured in the solid phases of HCl, HBr, and HI from 50° to 200°K. In solid I of each hydrogen halide two types of molecular motion have been detected: (1) a rapid rotational reorientation and (2) translational diffusion of the molecules. Solid III of HBr shows an intermediate plateau in the proton second moment and both HBr and HI have a well-defined minimum in the rotating-frame relaxation time T1ρ. These effects are interpreted as due to a single-plane reorientation process. Similar minima of T1ρ are observed in solid II of HI and the intermediate solid of HBr, which are ascribed to two-plane and three-plane reorientation processes. The splitting of the deuteron resonance of DBr and DI is quite dependent on temperature but not as strongly dependent as expected for equal site occupational probability. It is proposed that in the ferroelectric solid II of HCl the molecules undergo a single-plane reorientation process but with nonequal orientational site probabilities. Correlation times for these motions are compared with correlation times derived from dielectric loss measurements. The two sets of correlation time data are generally in order-of-magnitude agreement.

Molecular motion in succinonitrile and malononitrile by nuclear magnetic resonance

“…A more suitable analysis for T1 is that of Torrey [22] and Resing and Torrey [23]. In this analysis the interaction constant K is somewhat modified and the correlation function is not assumed to be exponential as was the case for equations (2) and (6). The general form of the result is little changed, however, especially if we are concerned, as we are here, with the case for tooT>> colt>> 1.…”

“…Secondly, were it not for the Tap measurements, we might have been tempted to ascribe the behaviour of T1 in this region as due to modulation of the intermolecular dipolar interaction by translational diffusion, in analogy to the well-established interpretation of such behaviour over a substantial temperature range in other plastic crystals [1,2]. However, for the available interaction of 0.7 G z the minimum value of T1 at 21.5 MHZ is 0.3 s and the deduced value of the correlation time at 10a/T=3 9 1 is about 3 x 10-9s which is unreasonably short and is quite inconsistent with the Tlp measurements which predict quite different values of T1 and TT when extrapolated to higher temperatures.…”

“…provides valuable information about the larger scale molecular motion particularly if taken together with other data such as for instance dielectric studies (if the molecule is dipolar). An excellent example of the power of this method is provided by the detailed studies of the various phases of the hydrogen halides which have been carried out in this and other laboratories [1][2][3].…”

Self-Diffusion Coefficients and Rotational Correlation Times in Polar Liquids. V. Cyclohexane, Cyclohexanone, and Cyclohexanol

“…From Eqs. (13) and (14) and Eq. (to) the anisotropy to be expected in T2 for dynamically coherent rotation may be evaluated.…”

“…T2 for the nCR model was calculated using Eqs. (10), (13), (14), and (17) Table IV will be discussed.…”