Alfred Büchler

Geometry of the Transition‐Metal Dihalides: The Fluorides of Manganese, Cobalt, Nickel, Copper, and Zinc

The deflection of mass spectrometrically detected beams of CaF2, MnF2, MnCl2, CoF2, NiF2, CuF2, ZnF2, ZnCl2, and HgCl2 by an inhomogeneous electric field has been examined. As found previously, CaF2 deflects in the manner expected for a polar molecule. The remaining molecules listed were found to be nonpolar. These observations are interpreted to imply that while CaF2 has a nonlinear equilibrium geometry the remaining species are linear. The result for HgCl2 is in agreement with a number of previous electron diffraction and spectroscopic studies.

Determination of the Geometry of Lithium Oxide, Li2O(g), by Electric Deflection

A conventional Inghram‐type mass spectrometer has been adapted to permit the study of the polarity of high‐temperature species by electric‐deflection methods. The molecule Li2O has been found to be nonpolar and therefore to have an equilibrium angle close to 180°, as shown by the absence of deflection of a molecular beam by an inhomogeneous electric field. The species LiO, which was found by Berkowitz, Chupka, Blue, and Margrave, has been confirmed to form a small percentage of the vapor in equilibrium with solid Li2O. Gaseous lithium molybdate, Li2MoO4, has been observed. It is readily formed by the reaction of lithium oxide with molybdenum above 1150°C.

Determination of Electronic Symmetry by Electric Deflection: LiO and LaO

The focusing, by means of an electrostatic quadrupole, of polar molecules with first‐ or second‐order Stark effects is discussed. Indications of molecular electronic symmetry may be obtained from quantitative measurements of the intensity of refocusing of beams of diatomic molecules. Such measurements indicate that the ground state of LiO is Π while that of LaO is Σ. It is suggested that the optical spectroscopic data of ScO, YO, and LaO are best explained by assigning the ground states of these three molecules as 2Σ. The observed low‐lying electronic states of these molecules are interpreted in terms of a localized‐orbital picture.

Mass‐Spectrometric Investigation of the Oxidation of Molybdenum and Tungsten

The oxidation of molybdenum and tungsten was investigated mass spectrometrically at temperatures between 1500° and 2600°K and oxygen pressures between 10—4 and 10—2 Torr. The principal products of oxidation were found to be the gaseous dioxide and trioxide, MO2(g) and MO3(g) (M=Mo or W). The trioxide is the more important species at low temperatures; the dioxide is the dominant product at high temperatures. Small amounts of polymeric oxides, (MO3)2(g) and (MO3)3(g) were formed at the lowest temperatures and highest oxygen pressures. The gaseous oxidation products are not in equilibrium with a solid surface oxide.

Infrared Spectra of Lithium Halide Monomers

The infrared spectra of the lithium halides have been re‐examined. The vibrational constants of the diatomic molecules are LiClωe=641±3ωexe=4.2±0.3LiBrωe=563.2±0.2ωexe=3.53±0.15ωeye=0.02±0.03LiIωe=498.2±0.2ωexe=3.39±0.15ωeye=0.08±0.03. The first five coefficients of the Dunham expansion of the potential energy have been obtained for lithium bromide and iodide. Rittners ionic model has been found to give a good representation of the potential energy. The ionic‐model treatment of the lithium halides has been extended to take account of the higher multipole polarizabilities of the halide ions. The introduction of quadrupole and higher polarizabilities destroys the agreement between observed and calculated spectroscopic constants which is found when only dipole polarizabilities are used.

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.

Gaseous Metaborates. I. Mass‐Spectrometric Study of the Vaporization of Lithium and Sodium Metaborates

The vaporization of lithium and sodium metaborate has been studied mass spectrometrically. The vapors of these compounds consist principally of the monomers LiBO2 and NaBO2, with some dimer and a very small amount of trimer also present. Heats of vaporization of the two metaborates and of boron oxide were determined with an effusion cell designed to give reliable second‐law heats. The values obtained are: B2O3(l)=B2O3(g)ΔHv,1300=93.6±3 kcal mole−1LiBO2(c)=LiBO2(g)ΔHs,1060=79±3 kcal mole−1LiBO2(l)=LiBO2(g)ΔHv,1160=70±3 kcal mole−12 LiBO2(g)=Li2(BO2)2(g)ΔH1120=−67±3 kcal mole−1NaBO2(c)=NaBO2(g)ΔHs,1070=73±3 kcal mole−12 NaBO2(g)=Na2(BO2)2(g)ΔH1070=−53±3 kcal mole−1.The composition and the dimerization energies of the metaborate vapors thus resemble those of the alkali halides, hydroxides, and cyanides.

Gaseous Metaborates. II. Infrared Spectra of Alkali Metaborate Vapors

The infrared spectra of gaseous lithium, sodium, and cesium metaborate have been examined between 2500 and 225 cm—1. Bands were observed at 1935 and 600 cm—1 for LiBO2, Li6BO2, NaBO2, and CsBO2, and at 2000 and 610 cm—1 for LiB10O2, NaB10O2 and CsB10O2. The two frequencies have been assigned to a stretching and bending vibration, respectively, of the metaborate BO2 group. Their similarity to the corresponding frequencies of the ion BO2— suggests a bond structure of the form M+(O—–B+–O—) for the alkali metaborates. The variation of the bonding of the BO2 group in a series of related compounds and the absence of alkali—anion stretching frequencies from the spectra of both alkali metaborates and cyanides are also discussed.

Gaseous Ternary Compounds of the Alkali Metals

Abstract : An extensive summary is given of the existing information on gaseous ternary salts of the alkali metals. Three groups of compounds are considered: (1) salts of monobasic acids or pseudohalides (e.g., hydroxides, metaborates, nitrates, perrhenates); (2) salts of dibasic acids (e.g., carbonates, sulfates); (3) mixed halides (e.g., LiBeF3, NaAlF4, KFeCl3). The identification of vapor species, structural data, and thermodynamics are discussed for each type of compound. Particular experimental problems and methods of data analysis are considered as they arise with reference to individual compounds.

Nanosecond Background Source for Flash Photolysis

A single-flash continuous spectrum producing more than adequate photographic density and having maximum intensity in the near ultraviolet is obtained in an argon–air mixture at elevated pressure by means of a light source1 of 20–30 nsec halfwidth. Tails of the light pulse are reduced by a distributed resistor which decreases the ringing of the current. The resistor is plated on the capacitor transmission line of the source. Absorption spectra show the usefulness of this source as a nanosecond spectroscopic background source for flash photolysis.