Probing Nonspecific Intermolecular Interactions with Noble Gas Nuclei

PROBING NONSPECIFIC INTERMOLECULAR INTERACTIONS WITH NOBLE GAS NUCLEI 

Relaxation times and medium shifts have been used to study intermolecular interactions between noble-gas atoms in the dilute gas all the way to the pure liquid and solid phases by He, Ne, Kr, Xe, and Xe NMR studies. In the case of Xe there have been additional studies of intermolecular interactions with foreign 

Even with 51 at. % Ne (highly enriched compared to the natural 0.26 at. % abundance), attempts to determine shifts of the Ne resonance in liquid and solid neon between 23 and 34 K were unsuccessful. The shifts were less than 1 ppm. On the other hand, chemical shifts in the gas, liquid, and solid phases of krypton and xenon have been observed. The results from several studies are summarized in Ref. 54. The absolute shielding of Kr or Xe nuclei in the dilute gas can be written as a virial expansion in the powers of the density p, as shown in Chapter 3  

Nuclear relaxation in the noble gases is different from polyatomic gases in that the relaxation mechanisms in the former have to be purely intermolecular rather than intramolecular. Thus, while Ti for polyatomic gases increase with increasing gas density above the Ti minimum (T, =kp), for the noble gases the opposite is true, i.e., l/T, = kp. 

The nuclear spin-lattice relaxation times in the pure gas, liquid, and solid phases have been measured for He, Ne (liquid and solid only ), 54,58) 

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