W. E. Falconer

Intermolecular potential between an atom and a diatomic molecule: The structure of ArCIF

Author Institution: Department of Chemistry, Harvard University; Bell Laboratories, Harvard University

Electric Resonance Spectroscopy of Hypersonic Molecular Beams

A hypersonic nozzle beam (Mach 19) of HCN molecules was studied by electric resonance spectroscopy. Translational temperatures of 4°K and rotational temperatures of 64± 30°K were found from a 283°K nozzle source. The monoenergetic character of the beam and the rotational cooling lead to an order of magnitude increase in signal‐to‐noise ratios. The absence of an appreciable velocity dispersion and a homogeneous radiation field allowed a critical comparison with theoretical two‐level resonance lineshapes. An SF6 diluent was used to reduce the beam velocity by one‐half and increase spectral resolution over a thermal (effusive) source. SF6 vibrational relaxation was observed. Chemically interesting species can be formed: ArXe, XeHCl, (HCl)2, (HCN)x, and (HF)x.

Electric Deflection of Molecular Beams of the Lanthanide Di‐ and Trifluorides, ScF3 and YF3

Electric‐deflection studies on molecular beams of the lanthanide trifluorides have been carried out in the temperature range 1000–1200°C. Substantial refocussing, indicative of polar distortions, has been observed for LaF3, GdF3, and LuF3. Weaker refocussing was present in TmF3. CeF3 and ErF3 showed refocussing barely above the noise level. Defocussing was observed in PrF3, NdF3, TbF3, DyF3, and HoF3. Observations on SmF3, EuF3, and YbF3 were inconclusive due to sample reduction in the oven but showed no refocussing attributable to the respective trifluorides. ScF3 and YF3 showed refocussing of a magnitude similar to the trifluorides of La, Gd, and Lu. Deflection studies on the three known lanthanide difluorides revealed that SmF2, EuF2, and YbF2 are strongly polar molecules in the vapor phase and must, therefore, have highly bent structures.

Molecular Structure of XeF6 and IF7

The deflection of molecular beams of XeF2, XeF4, XeF6, and IF7 in an inhomogeneous electric field has been examined. From the defocusing behavior of each of these species, it is concluded that the electric dipole moment μ is less than 0.03 D for XeF4, XeF6, and IF7 if these molecules have rigid structures. The upper limit for the polarity of nonrigid (inverting) structures is (μ / Δ1 / 2) < 0.1 D / (cm−1) / 2, where Δ is the separation between inversion doublets. These results imply molecular structures with symmetry‐forbidden electric dipole moments for XeF4, XeF6, and IF7.

Gas-phase structures and mass spectra of binary pentafluorides

Abstract Most known non-radioactive pentafluorides have been examined by molecular-beam mass spectrometry and by the deflection of molecular beams in inhomogeneous electric fields. Extensive association of the vapors occurs for all but the lighter pentafluorides and the interhalogens. The interhalogen pentafluorides are strongly polar, consistent with the accepted C4v symmetry. The transition-metal and Group V pentafluorides are all non-polar, except VF5 and CrF5 for which temperature-dependent polarity is observed. However, uncertainty exists as to whether these observations are applicable to monomeric pentafluorides in all cases. Mass-spectral cracking patterns are presented for all species.

Comparison of Radical and Nonradical Processes in the Condensed‐Phase Radiolysis of n‐Hexadecane

The effects of state, temperature, and chemically reactive solutes on the radiolysis of n‐hexadecane in condensed phases have been examined. All product yields are reduced by radical scavengers in liquid‐state n‐hexadecane, but only dotriacontane isomers are reduced in the solid. Iodine acts as a chemical scavenger and is more effective than 2‐methylpentene−1. A hot‐hydrogen‐atom mechanism, together with molecular elimination, accounts for the formation of most of the hydrogen in the irradiation of n‐hexadecane. Low‐molecular‐weight products are formed entirely by molecular reactions in the solid‐state radiolysis and, about equally, via molecular and radical processes in the liquid. Intermediate‐molecular‐weight products in the liquid radiolysis are 80% from combinations of radicals from chain scission with various hexadecyl radicals. The remaining 20% in the liquid and the total intermediate yield in the solid are from nonradical processes. The combination of hexadecyl radicals yields at least 40% and 70...

Crossed‐molecular‐beam study of the kinematics and dynamics of charge‐transfer collisions

Using a crossed‐molecular‐beam apparatus, the low energy product ions formed in a variety of resonant and near‐resonant charge‐transfer collisions at incident ion energies of 200 eV have been examined. Observation of the translational energy and angular distributions of these low energy product ions confirms that charge transfer takes place at large impact parameters with near‐zero momentum transfer.

Syntheses and raman spectra of nitrosyl fluorometallate salts

Abstract Nitrosyl salts containing MF - 6 , MF = 6 , MF ≡ 6 , MF - 7 and MF = 8 (M = Cr, Mo, W, Re, Rh, Ru, Os, Ir, Pd, Pt, and Ru) have been synthesized using NOF + F 2 or NO with the appropriate metal or metal fluoride as reactants. All of the compounds were characterized by their Raman spectra and each spectrum was analysed in terms of the fundamental vibrations of cations and anions. Analysis of the Raman spectra of the product formed in the reaction of NOAuF 6 with NOF and F 2 lead to the conclusion that (NO) 2 Au(IV)F 6 is a reaction product.

Polar Distortions in ReF7 and IF7

The deflection of molecular beams of ReF7 and IF7 by inhomogeneous electric fields has been studied as a function of temperature. Polar components were readily observed in molecular beams of ReF7, and their intensity increased as the temperature was lowered. A similar effect was just observable for IF7 at the lowest temperatures attainable. These observations show that the heptafluorides do not have rigid polar structures, but they are compatible with nonrigid distorted geometries for ReF7 and IF7.

Water Cluster Ions: Formation and Decomposition of Cluster Ions in the Oxygen‐Water System

Drift‐tube techniques have been employed to determine rate constants in the reaction sequence leading to formation of the hydronium ion hydrates H3O+(H2O)n starting from O2+ ions in O2–H2O gas mixtures at 310°K. Total pressures used ranged from 0.5 to 2 torr with water partial pressures from 0.15 to 1.2%. Measured three‐body clustering rate constants declined in all cases as E/P0 increased in the range 5–30 V cm−1· torr−1. Thermal rate constants were deduced from the low E/Po data. Mobilities for O2+ and H3O+(H2O)n in oxygen are given as a function of E/Po in the range 5–60 V cm−1· torr−1 and for O2+ and H3O+ in argon from 4 to 20 V cm−1· torr−1. In oxygen, quasiequilibrium studies were conducted in which a cluster ion H3O+(H2O)n loses one or more water molecules during drift, successive ions from n=3 to 0 becoming dominant as E/Po increased from 5 to 60 V cm−1· torr−1. A simple analytical model for treating sequential reactions in drift experiments is presented.