W. R. M. Graham

Fourier transform infrared isotopic study of linear CrC3: Identification of the ν1(σ) mode

A vibrational fundamental of linear CrC3 has been detected in the products from the laser ablation of chromium and carbon rods trapped in solid Ar at ∼10K. Fourier transform infrared measurements of frequencies and C13 isotopic shifts are in very good agreement with the predictions of density functional theory calculations at the B3LYP∕6-311G+(3df) level, resulting in the identification of the ν1(σ) stretching mode at 1789.5cm−1. This is the first optical detection of the linear isomer of the transition-metal carbide CrC3 for which previous photoelectron spectroscopic studies have reported evidence of both linear and cyclic isomers.

Characterization of P. R. Spring (Utah) tar sand bitumen by the EPR technique; free radicals

Bitumen and its heptane-asphaltene and heptane-petrolene fractions extracted from P.R. Spring (Utah) tar sand have been investigated using EPR at 9.2 GHz. In each case a single, structureless EPR transition is observed at g≈2 due to organic free radicals. From the temperature dependence of the free radical spectrum at 10–300 K, it is argued that, in addition to monoradicals, exchange coupled spins exist in all three fractions which result in a singlet ground and a triplet excited state. The origin of the exchange interaction, which is isotropic, is discussed in terms of the presence of similar heteroatoms in alternate aromatic sheets. The separation, Δ=127 ± 1 cm −1 , between singlet and excited triplet states for all three fractions indicates a similar core structure which is consistent with Pfeiffer and Saals model for bitumen. Oxygen and/or air causes a reversible enhancement of the free radical signal for asphaltene which is explained in terms of enhanced exchange coupling. An irreversible change in the asphaltene structure is observed to take place on subjecting it to a thermal cycle of 292-500-292 K, indicating a complex reorientation of the structure during cooling.

Vibrational spectrum of cyclic TiC3 in solid Ar

The Fourier transform infrared spectrum of TiC3 was observed by trapping the vapor produced during dual Nd:YAG laser ablation of Ti and C rods in solid Ar at approximately 9 K. Measurements of frequencies and 13C isotopic shifts have enabled the identification of the fanlike (C(2v)) isomer of TiC3 with fundamental vibrations nu3(a1) = 624.3 and nu5(b2) = 1484.2 cm(-1). A third fundamental nu4(b1) has been tentatively identified at 573.8 cm(-1). The results are in good agreement with the predictions of density functional theory calculations at the B3LYP6-311G(3df,3pd) level. The observed C(2v) structure and the observed nu3 metal-carbon stretching mode are also consistent with earlier results from photoelectron spectroscopy.

Origin of the Mn2+ e.p.r. spectrum in Pittsburgh No. 8 bituminous coal

Abstract The e.p.r. and i.r. spectra of hand-picked samples of calcite from Pittsburgh No. 8 coal, show that it contains the Mn 2+ paramagnetic ion and clay minerals as impurities. Furthermore, comparison of the e.p.r. spectra of hand-picked and natural calcite shows that the Mn 2+ spectrum in this coal originates from calcite, which when diluted in KBr or coal produces a spectrum similar to that reported by other investigators. The results obtained when coal-derived calcite was treated with dilute H 2 SO 4 and HCI rules out the possibility that the Mn 2+ originates from the pyrite or clays present in the coal.

Fourier transform infrared observation of the ν1(σ) mode of linear CoC3 trapped in solid Ar

Fourier transform infrared (FTIR) and density functional theory (DFT) isotopic studies on cobalt-carbon species have resulted in the detection of linear CoC3. Dual laser ablation of carbon and cobalt rods, followed by trapping the products in solid Ar at ∼10K, produced the CoC3 chain. FTIR measurements of C13 isotopic shifts are in good agreement with the predictions of DFT calculations using the B3LYP and BPW91 functionals and the 6-311+G(3df) basis set, confirming the assignment of the ν1(σ) fundamental of linear CoC3 at 1918.2cm−1.

Vibrational spectra of germanium–carbon clusters. I. Identification of the ν3(σu) mode of linear GeC3Ge

The first germanium–carbon cluster GeC3Ge, has been detected in the products from the laser evaporation of carbon and germanium rods trapped in solid Ar at ∼10 K. On the basis of very good agreement between Fourier transform infrared (FTIR) measurements and the predictions of density functional theory (DFT) calculations for the frequencies and 13C isotopic shifts, the ν3(σu) mode of linear GeC3Ge has been identified at 1920.7 cm−1.

The vibrational spectrum of fanlike ScC3 in solid Ar

Fourier transform infrared spectra of fanlike (C(2v)) ScC(3) have been obtained by trapping the vapor from the Nd:YAG (yttrium aluminum garnet) laser ablation of (13)C-enriched graphite and Sc rods in solid Ar at approximately 10 K. Three vibrational fundamentals, the nu(5)(b(2))=1478.0 cm(-1) asymmetric carbon stretch, the nu(3)(a(1))=557.0 cm(-1) symmetric metal-carbon stretch, and the nu(1)(a(1))=1190.7 cm(-1) symmetric carbon stretch have been observed for the first time. The measured isotopic spectra are in good agreement with DFT-B3LYP/6-311G(3df,3pd) simulated spectra and indicate a (2)A(2) ground state rather than (4)B(1) as suggested by other theoretical calculations. The frequency of the nu(3)(a(1)) fundamental is consistent with a frequency of 560+/-30 cm(-1) reported in a photoelectron spectroscopy investigation of ScC(3).

Identification of the ν1(σ) mode of linear GeC3Si

The first optical observation of a mixed germanium-silicon-carbon (GelSimCn) cluster has been made by trapping the products of the laser ablation of carbon/silicon/germanium rods in Ar at 10 K. The ν1(σ) C–C stretching mode of linear GeC3Si has been identified at 1939.0 cm−1. The assignment is confirmed by the very good agreement between Fourier transform infrared (FTIR) measurements of frequencies and isotopic shifts and predictions of our quantum theoretical calculations.

Characterization of Circle Cliffs tar sands. 1. Application of the FT-i.r. technique to mineral matter

Abstract In the first of a two-part study of mineral matter associated with tar sands, results are presented from the characterization of samples from the Circle Cliffs and P.R. Spring deposits using FT-i.r. spectroscopy. Following the collection of data for a library of minerals associated with tar sand deposits, the procedures used in the analysis were tested on mineral mixtures of known composition. Illite, dolomite, kaolinite and quartz were measured in the Circle Cliffs sample, while the only minerals present in the P.R. Spring specimen were microline feldspar and quartz.

Fourier transform infrared observation of the ν3(σu) vibration of NiC3Ni in solid Ar

The Fourier transform infrared spectrum of linear NiC(3)Ni was observed by trapping the vapor produced from the dual ablation of nickel and carbon rods with Nd:YAG (yttrium aluminum garnet) lasers in solid Ar at approximately 10 K. Measurements of (13)C isotopic shifts have enabled the identification of the nu(3)(sigma(u)) vibrational fundamental at 1950.8+/-0.2 cm(-1), an asymmetric carbon stretching mode. Experimental results are in good agreement with the predictions of density functional theory at the B3LYP6-311G(*) level. Theoretical results suggest that the molecule is slightly floppy. Although other nickel carbide clusters have been studied theoretically or observed by photoelectron spectroscopy or mass spectrometry, this is the first report on the structure of NiC(3)Ni and its vibrational spectrum.