Showing papers by "Lester Andrews published in 1983"

Infrared spectra of OC–HX hydrogen‐bonded complexes in solid argon

Abstract: The hydrogen‐bonded complexes OC–HX (X=F, Cl, Br) has been prepared by condensing Ar/HX and Ar/CO reagent mixtures at 12 K. FTIR spectra of the complexes are characterized by strong H–X absorptions (νs) displaced below the isolated HX fundamental, strong C–O absorptions displaced above the isolated CO fundamental, and sharp degenerate librational modes (νl) in the far infrared. Observation of a single degenerate νl mode indicates linear structures for the complexes. The displacements Δνs and ΔνCO for the complexes decrease in magnitude in the series HF≳HCl≳HBr in direct relationship with the trend in hydrogen bonding strength for the hydrohalic acids.

FTIR spectra of water–hydrogen fluoride complexes in solid argon. Evidence for inversion doubling in the HF librational modes of H2O– –HF

Abstract: Co‐condensation of dilute Ar/HF and Ar/H2O samples at 12 K produces a number of sharp new infrared absorptions. The major species, which exhibits a strong 3554.7 cm−1 band and two quartets beginning at 753.1 and 635.6 cm−1, is identified as H2O– –HF. Isotopic substitution in the base submolecule changes the splitting in the latter multiplets and provides evidence for inversion doubling of the H–F librational modes in the H2O– –HF complex. The reverse complex HF– –HOH, identified at 3915.5 cm−1, exhibits a stronger interaction when HOH is replaced by DOD. Two H–F stretching fundamentals, which show small D2O shifts, increased markedly on sample warming and are assigned to the 1:2 complex H2O– –HF– –HF with an open structure.

Matrix reactions of molecular oxygen and ozone with aluminum atoms

Abstract: Frozen matrices of N/sub 2/ or Ar containing small concentrations of Al atoms and O/sub 2/ or O/sub 3/ have been prepared by matrix isolation techniques and studied by infrared absorption spectroscopy. The spectra were analyzed on the basis of isotopic oxygen substitution, variations in the concentrations of reagents, and changes in band intensities after reagent diffusion and reaction in the matrix. These analyses have shown that the principal reaction product in N/sub 2/ matrices with either O/sub 2/ or O/sub 3/ was an asymmetrical and highly bent aluminum dioxygen molecule, AlOO (C/sub s/). Very little of this species was produced in Ar matrices. The stretching modes of AlOO in N/sub 2/ were identified as 1337 cm/sup -1/ for nu/sub 1/(O-O) and 1091 cm/sup -1/ for nu/sub 3/(Al-O). Metal ozonides absorbing in the region of 850 cm/sup -1/ also were produced by both oxygen reagents in both N/sub 2/ and Ar matrices. Several other complex species were identified as additional reaction products. No bands could be identified as belonging to a metal superoxide species, which is the principal product in the matrix reactions of Ga, In, and Tl with O/sub 2/. 24 references, 4 figures, 3 tables.

FTIR observation of the N2‐‐‐HF complex in solid argon

Abstract: Sharp absorptions at 3881.5 and 262 cm−1 in argon matrices containing HF are shown to depend upon N2. Substitution with DF indicates assignments to the νs and νl modes of the linear N2‐‐‐HF complex.

Infrared spectrum of the CO2–HCl complex in solid argon at 12 K

Abstract: Co‐condensation of CO2 and HCl in excess argon at 12 K produced the CO2–HCl hydrogen‐bonded complex. Small shifts in the νs and ν3c modes, the low νl fundamental, and a very weak infrared Fermi doublet indicate a weakly bound complex. The more strongly bound CO2–HF and C 18O2–HF complexes gave more intense infrared Fermi doublets. The infrared intensity ratio ν3/ν1 is 200/1 for the CO2–HF complex demonstrating that the HF ligand induces finite electrical asymmetry in the CO2 submolecule.

Absorption spectra of substituted biphenyl and related cations in solid argon and a comparison with photoelectron spectra

Abstract: One-photon and two-photon matrix photoionization experiments have been performed with substituted biphenyls, fluorene and 9,10-dihydrophenanthrene. Absorption spectra in the red region correlate with photoelectron spectra for a π3→π6 transition and indicate a relaxation of the dihedral angle upon ionization. Sharp ultraviolet absorption spectra are assigned to π→π* transitions for the matrix-isolated cations.

Absorption spectrum of the carbon tetrachloride molecular cation in noble-gas matrices

Abstract: Carbon tetrachloride diluted in argon, krypton or xenon and subjected to vacuum-ultraviolet radiation during and after condensation gave strong photosensitive absorptions at 425, 430 and 455 nm, respectively, which are assigned to CCl4+. This study suggests that absorptions in this region following radiolysis of CCl4 in hydrocarbon glasses are probably due to CCl4+ as well and that structural relaxation follows ionization of CCl4 in the solid phase.

A spectroscopic study of the ground states of CHCl+2 and CDCl+2 using a new multichannel detector photoelectron spectrometer

Abstract: The first photoelectron bands of CHCl2 and CDCl2 produced by F atom reactions with CH2Cl2 have been observed with a new multichannel detector photoelectron spectrometer. Vibrational structure was resolved on each band; the vertical ionization energy and v′=0−1 ionic vibrational spacing were measured as 8.54±0.01 eV and 860±30 cm−1 for CHCl2 and 8.52±0.01 eV and 790±30 cm−1 for CDCl+2 vibrational interval is in agreement with a weak chlorine isotopic triplet absorption observed at 845 cm−1 in solid argon and assigned to the symmetric C–Cl2 stretching mode of CHCl+2.

Absorption spectra and photochemical rearrangements of the 1,2-benzotropylidene molecule and parent cation in solid argon

Abstract: Photolyse UV proche et lointaine de benzo-1,2 tropilidene en matrice d'argon. Transposition en benzonorcaradiene et en isomere du methylnaphtalene sous rayonnement UV proche. Sous rayonnement UV lointain formation du cation parent du benzotropilidene (a 20300 cm −1 ) en accord avec le spectre calcule par la methode CNDO. Par photolyse dans le visible transposition du cation parent en cation benzonorcaradiene et en cation hydro-1 methylene-2 naphtalene

Infrared Absorption Spectra of Molecular Ions in Solid Argon

Abstract: Molecular ions are of considerable chemical and physical interest for comparing the spectroscopic and bonding properties of neutral molecules with their positive and negative molecular ions. The study of molecular ions in the gas phase by photoelectron, photoionization mass and ion cyclotron resonance spectroscoies can be complemented by infrared and optical absorption spectra of the molecular ion trapped in a solid inert gas host. Further ion studies with tunable infrared lasers will be greatly aided by the vibrational data obtained for molecular ions in noble gas solids. The ion-matrix interaction is of fundamental and practical interest as matrix spectra of ions are related to the gas phase.

The absorption spectra of the phenoxyl radical in solid argon

Abstract: Vacuum ultraviolet photolysis of phenol, phenol-d 6 and anisole during condensation with excess argon at 20 K has produced and trapped the phenoxyl radical as evidenced by structured absorptions at 397.2 and 628.1 nm. A broad photosensitive 416 ± 2 nm band is tentatively assigned to the phenol cation.

Visible and Ultraviolet Spectra and Photochemistry of Molecular Ions in Solid Argon

Abstract: Optical spectroscopic studies of molecular ions in solid argon [1] provide information on electronic states and ion structure which are complementary with studies in rigid organic glasses [2], ultraviolet photoelectron spectra (PES) [3], and photodissociation spectra (PDS) [4]. Spectra in solid argon are generally sharper and provide more vibrational information than glass spectra, and the cryogenic matrix quenches internal energy thus producing sharper bands than PDS and allowing the stabilization of facile molecular ions. The solid argon host also moderates photodissociation and allows isomerization to be a competitive process.