We have succeeded in obtaining infrared spectra of molecules adsorbed on the surface of clusters. The method is based on the photodissociation spectroscopy technique developed in our laboratory for the study of cluster beams and on a simple but effective way to prepare mixed clusters in which an IR chromophore is attached to the surface of a nonabsorbing host cluster. The possible extension of this technique to the study of molecular spectroscopy at the surface of clusters large enough to simulate crystal and liquid surfaces is also discussed.

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The proton magnetic resonance spectra of cation-exchange resins of crosslinkage XI to XI6 in the H +, Li', N a + , K -, R b + , Cs +, and NH,' forms have been recorded and the values of the molal chemical shift, 6, , +O, are found to be -0.321, -0.005,0.041,0.031,0.028,0.015, and 0.00 (assumed) p.p.m./mole, respectively, for the cations. These values are very nearly equal to those observed in corresponding aqueous solutions, indicating that ion-solvent interactions are similar in both the resin matrix and the aqueous solution. The temperature dependence of the chemical shift shows the same trend. The effective hydration numbers calculated from the temperature dependence are 2.0 (4.81 m ) for the H + form, 4.8 (3.25 m) and 3.6 (5.26 177) for the Na' form, 4.4 (3.9 m) for the K + form, and 2.4 (6.18 171) for the Cs+ forsn. The ions in the resin phase behave as solutions of strong electrolyte, which is consistent with the polyelectrolyte gel model for the ion-exchange resin.Canadian Journal of Chemistry, 48, 917 (1970) Introduction Nuclear magnetic resonance (n.1n.r.) has bee11 exte~lsively applied to the study of ionic solvation and three reviews (1-3) serve to indicate the extent and scope of present interest in the field. The n.m.r. studies fall into four categories: measurements of (i) reiaxation times, (ii) peak areas. under suitable, though unfortunately uncommon, conditions, solvent exchange may be slowed down sufficiently to allow the observation of cationic solvation shells, leading to a direct determination of the primary solvation number of the cation (4). In contrast, solvation numbers determined by observation of che~nical shifts in electrolyte solutions have a less obvious sigilificauce, since both cationic and anionic effects contribute to the chemical shift. Malinowski and co-workers (5-7) have performed a series of such experiments, observing the proton chemical shift of aqueous electrolyte solutions a t several temperatures and obtaining an "effective" solvation number.It is of interest to perform similar experiments on ion-exchange resin in as q~~arltitative a manner as possible, so that insight may be gained as t o the environ~iients of the ionic species within the resin.Experimental

Infrared spectra of supersonic jets of carbon dioxide seeded in helium are reported: Features assignable to clusters were observed for the ν2, ν3, ν1+ν3, and 2ν2+ν3 bands. A detailed study was made of the ν3 band, from which it was concluded that the clusters do not adopt the face-centered cubic crystal structure of solid carbon dioxide. The observed spectra indicate that the cluster geometry is largely determined by pairwise interactions between adjacent molecules. Furthermore, expansions of pure carbon dioxide produced clusters whose spectra indicate motional averaging: such clusters seem to be fluid on a picosecond time scale.

An apparatus is described in which a supersonic beam of nitrous oxide in helium impinges upon a 2 °K silicon bolometer, or alternatively, is detected by a mass spectrometer. Laser excitation of the beam in the vicinity of ν3 of nitrous oxide decreases the flux of the van der Waal’s molecule (N2O)2 reaching the bolometer. Thus, excitation of ν3 is followed by vibrational predissociation of the van der Waal’s bond.

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Intense infrared absorptions of small particles suspended in a dissimilar medium show effects that allow one to deduce, at least in principle, the morphology of the particles. These effects have their origins in the discontinuity in optical constants at the surface of the particle, and may be described analytically when the particles are spherical or ellipsoidal. This paper addresses the problems that arise when the particles under consideration are crystalline and have sharp edges and corners. Analytical descriptions are not available for such cases and it is shown that a numerical implementation the current standard electrostatic approach does not converge for cubes. However, convergence can be obtained by chamfering the edges and corners of the simulated particle. Experimental spectra are reported for suspended microcrystallites of sulfur hexafluoride and of carbon dioxide. The spectra were simulated using a variety of morphologies and it is concluded that the sulphur hexafluoride particles were cubes while the carbon dioxide particles were cuboctahedra.