Ian R. Beattie

Vibrational analysis of the 460 nm band system of nickel dichloride produced in a free jet expansion

Using a free‐jet expansion which incorporates a heated nozzle, we have recorded the laser excitation spectrum of the 460 nm band system of NiCl2 at a rotational temperature of ∼40 K. 35Cl/37Cl isotope shifts were resolved which permit the assignment of progressions involving the symmetric stretching vibrational mode and identify a triplet splitting with spacings of 96 and 149 cm−1 which is believed to be due to spin–orbit coupling. Sequence bands involving the bending vibrational mode are also tentatively assigned. Only a small change in the symmetric stretching vibrational wave number is found between the electronic states involved in this transition (ν’1 =356 cm−1, ν″1 =360 cm−1). This result and the triplet splitting observed are discussed with respect to the possible electronic states involved and the assignment of this band system as either a Laporte forbidden g↔g transition involving the d orbitals on the Ni atom or an allowed u↔g charge transfer transition.

A Critical Appraisal of the Experimental Data on the Molecular Structure and Spectra of Halides, Oxides, and Hydrides of the s-, d-, and f-Block Elements.

Evidence for unusual shapes of simple MX(n) molecules that are not stable under normal conditions is critically appraised in this review, which assesses current knowledge of the spectra and structures of many simple binary halides, oxides, and hydrides. It emphasizes the need for more high-resolution gas-phase spectroscopic data, summarizes the current state of knowledge in many fields, and suggests key experiments that should be carried out to resolve conflicting results obtained in earlier studies.

Micro-Raman spectroscopy in the Earth Sciences

When a monochromatic (i.e. single-frequency) beam of light traverses a medium (gas, liquid or solid) the majority of the scattered light will remain at the incident frequency. However, a small proportion of the scattered light will be at changed frequencies, above and below the incident frequency, and this is referred to as the Raman effect. The Raman effect was first observed by Raman and Krishnan (1928) using focused sunlight and filters and relied on the visual observation of colour changes in the scattered light. However, it was not until the advent of continuous wave visible lasers, during the 1960s, that the importance of Raman spectroscopy as a routine analytical technique was realized. Furthermore, the availability of this highly intense monochromatic light source, which could be focused to a narrow waist, allowed the analysis of small volumes of gas, liquid or solid.

The interaction of some metal dichlorides (Ca, Cr, Mn, Fe, Co, Ni, Zn) with dinitrogen

Abstract The dichlorides of Ca, Cr, Mn, Fe, Co, Ni and Zn have been isolated in argon and nitrogen matrices and examined by infrared spectroscopy in the range 4000-200 cm −1 . The results obtained are discussed in relation to the behaviour of the difluorides and the monoxides. Both CoCl 2 and NiCl 2 show anomalous shifts in the frequency of v 3 between argon and nitrogen matrices. Isotopic substitution shows that these molecules are strongly bent in nitrogen matrices, in contrast to their behaviour in argon matrices. It is likely that the primary interaction between the host nitrogen matrix and the guest dichloride is ion—induced-dipole rather than the formation of a discrete MCl 2 ·N 2 species.

Vibrational structure in the laser excitation spectrum of nickel dichloride at 360 nm

Abstract Nickel dichloride has been formed “cold” in the vapor phase by heating the solid to about 750°C, entraining the vapor in a high pressure of argon and expanding it supersonically through a small hole into a vacuum chamber. The laser excitation spectrum of the sample prepared in this way has been recorded in the region of 360 nm. Under these conditions, it is possible to resolve both vibrational and rotational fine structure. The same spectrum was recorded when carbon tetrachloride vapor was passed over the hot metal and expanded through the nozzle. Some “hot” bands have been identified by dispersing the fluorescence with a small monochromator. Virtually no chlorine isotope structure could be identified, even when isotopically enriched samples were used. A partial analysis of the vibrational structure has been achieved in which several progressions in the symmetric stretching vibration have been identified. These progressions are consistent with a value for v 1 of 360 cm −1 for the lower electronic state and 345 cm −1 for the upper electronic state. The complications in the observed spectrum may be caused by two or more upper electronic states being involved in the band system.

the dispersed fluorescence of nickel dichloride under molecular beam conditions: A determination of ground-state vibrational intervals

Abstract Cold nickel dichloride, NiCl2, has been produced in a supersonic beam by expansion of its vapour through a heated nozzle. Fluorescence has been excited with the 364 nm line of an argon ion laser and dispersed to reveal extensive vibrational progressions of 357 cm−1 at spacings of 177, 401 and 1026 cm−1 from the laser frequency. These have been assigned to the symmetric stretching frequency (ν1 = 357 cm−1), twice the bending frequency (2ν2=177 cm−1) and twice the antisymmetric stretching frequency (2ν3 = 1026 cm−1). No definite assignment for the 401 cm−1 interval can be suggested.

A quantitative study of the aluminium trichloride–acetonitrile system using X-ray crystallography, electrical conductivity, aluminium-27 and chlorine-35 nuclear magnetic resonance and Raman spectroscopy. The characterization of the pentakis(acetonitrile)chloroaluminium(III) ion in the solid state and in solution

The compounds MCl3(M = Al, Ga, or In) yield electrically conducting solutions in acetonitrile. Boron trichloride gives non-conducting solutions and, contrary to previous work, this is interpreted as due to the presence of a molecular solute BCl3·MeCN. The electrical-conductivity data for AlCl3 in acetonitrile are discussed in detail and it is shown that from the results obtained it is not possible to differentiate between 1 : 1 and 1 : 2 electrolyte behaviour. Quantitative Raman and 27Al n.m.r. spectra demonstrate that ca. 70% of the aluminium in solutions of AlCl3 in acetonitrile is present in the form of [AlCl4]–. An X-ray single-crystal study of the solid adduct AlCl3·2MeCN crystallizing from such a solution shows that this adduct is correctly formulated as the auto-complex [AlCl(NCMe)5]2+2[AlCl4]–·MeCN. Further 27Al n.m.r. studies on solutions of Al[ClO4]3 in acetonitrile and of the solute AlCl[ClO4]2, in conjunction with the work on AlCl3 demonstrate that [AlCl(NCMe)5]2+ is the major cationic constituent of aluminium trichloride solutions in acetonitrile. The electrical-conductivity, Raman, and n.m.r. data on these solutions are all satisfactorily interpreted by the principal ionization scheme [AlCl(NCMe)5]2+2[AlCl4]– which is the formulation found for the crystal. The ionization of AlCl3, but the non-ionization of BCl3, in solution in acetonitrile is attributed principally to the ability of aluminium to adopt a co-ordination number of greater than four in ions such as [AlCl(NCMe)5]2+.

Raman Spectrum of Antimony Pentafluoride in the Gaseous Phase as a Function of Temperature. Evidence for a Trigonal Bipyramidal Shape for the Monomeric Species

The gas phase Raman spectrum of antimony pentafluoride as a function of temperature shows clearly the dissociation of a polymeric species. The infrared spectrum of the gas (under conditions where the Raman spectrum shows no evidence for the presence of monomer) is closely similar to that of the liquid. This spectrum is also similar to that found in previous matrix isolation studies when monomer was thought to be present. It is likely that the earlier assignment of a C4v shape to monomeric antimony pentafluoride is erroneous.

Nuclear hyperfine structure in the electronic spectrum of CuCl

The (0,0) bands of the D 1Π-X 1Σ+ and E 1Σ+-X 1Σ+ transitions in CuCl have been recorded by laser excitation spectroscopy. The sample was vaporized in a high temperature nozzle an then cooled by supersonic expansion into a vacuum chamber. The observed rotational temperature was about 15 K. Hyperfine structure for the copper nucleus was easily resolved in the D-X transition. The spectra have been analysed and fitted to appropriate effective hamiltonians. Several molecular parameters have been determined in least-squares fits of the hamiltonian to the data. The implications of these values for the structure of CuCl are discussed. In particular, it is suggested that the D state conforms more closely to a 1Π state than a 3Δ1 state, in contradiction to some theoretical calculations.

Interatomic distances for some first row transition element dichlorides isolated in cryogenic matrices using x‐ray absorption fine structure spectroscopy

X‐ray absorption fine structure (XAFS) data for several 3d transition metal dichlorides isolated in nitrogen, argon, or methane matrices have been collected and analyzed. The bond lengths obtained are in reasonable agreement with those from vapor phase electron diffraction. The results are briefly discussed with reference to Badger’s rule extended to triatomics.