A procedure for determining the allowed local site symmetry groups S for surface adsorbed molecules is presented. An analogy can be drawn between the perturbing field experienced by a matrix isolated molecule in a three-dimensional crystal and that experienced by a molecule adsorbed on a surface. In the former case the field has the symmetry of the host lattice site whereas in the latter case the field has the symmetry of the adsite. If the surface is viewed as a homogeneous two-dimensional plane, then the symmetry of the adsite is described by the group G = C∞v. If the surface cannot be viewed as an unstructured homogeneous plane so that the perturbing field experienced by the adsorbed molecule must be considered on a microscopic level, then the adsite symmetry will be described by the group appropriate for the substrate atoms. This can only be one of the groups G = Cn or G = Cnv. The symmetry operations of the local site symmetry group S consist of an operation in the molecular point group M applied to the molecule combined with an operation in G applied to the substrate. A mapping of the operations in M and G to operations in their isomorphous Longuet-Higgins groups allows the operations to be identified as permutation P or permutation–inversion P operations. The operations in S are restricted to be combinations of P operations in M with P operations in G and P operations in M with P operations in G. An adsorbed molecule having M = D3h symmetry is used as an example to demonstrate the procedure for determining S. The local site symmetry group of the adsorbed molecule is, in general, different for the homogeneous surface approximation as opposed to the microscopic surface approximation. An attempt is made to apply predicted spectroscopic selection rules to adsorbed pyridine and ethylene. Several factors which complicate the interpretation of Raman spectra of molecules adsorbed on metal surfaces are discussed, one of these being depolarization effects due to rough surfaces.

The vibrational frequencies of halogens adsorbed on Ag(100) are calculated. The frequency of a single adsorbed atom vibration perpendicular to the surface is obtained from AgX (X=F, Cl, Br, I) crystal frequencies. Interaction between dipoles consisting of the effective charge on the adsorbed atom and its induced image charge produces a coverage dependent frequency. The effective charge on the adsorbed atom is assumed to be 1.0e, while the electronic polarizability of the real-plus-image atom system is assumed to be twice the electronic polarizability of X−. At full coverage, the calculated frequencies for the k=0 modes are 437, 241, 150, and 113 cm−1, respectively, for X=F, Cl, Br, I, which compare well with experimental values, and these frequencies are assigned to external vibrational model of halogen atoms adsorbed on silver.

Internal optic mode dispersion curves and frequency distribution functions in dipole coupled crystals: Applications to NaN3 and KBrO3The internal optic modes of Br0 3 -and Cl0 1 -ions are studied in a series of NaCl0 3 /NaBr0 3 mixed crystals over the entire relative concentration range. Raman spectra and near-normal incidence infrared reflectivity spectra of single mixed crystals and Raman spectra of microcrystalline mixed crystal powders are presented and discussed. Mode mixing of the VI and V3 modes of Br0 3 --was studied as a function of concentration, and a near accidental degeneracy of VI and V3 was noted in the high dilution limit of matrix isolated Br0 3 -in a host NaCl0 3 crystaL

Corrosion and stress-corrosion cracking (SCC) tests were performed on aluminum drillpipe Alloy 2014-T6 in a waterbased, low-solids, nondispersed (LSND) drilling mud. Variables examined included chloride concentration, temperature, state of aeration, and effects of galvanic coupling to tool-joint steel. Electrochemical corrosion test results suggested that the aluminum alloy has adequate corrosion resistance to at least 71°C [160 0 P], even when it is galvanically coupled to steel in aerated muds. However, SCC susceptibility of the alloy in aerated muds was clearly demonstrated by slow-strain-rate and rising-stress-intensity/SCC tests. SCC did not occur in deaerated muds. We concluded that oxygen scavenging and monitoring are important to the successful performance of aluminum alloy drillstrings in chloride-containing, water-based, LSND drilling muds. These conclusions were confirmed by excellent field performance. IntroductionA highly deviated well (Fig, I) was recently drilled from a fixed offshore platform. The well was kicked off at 427 m [1,400 ft], and angle was built at a rate of 1.5°/30 m [1.5°1100 ft] to an inclination of 58° from vertical at 1615 m [5,300 ft] measured depth (MD) and 1416 m [4,846 ft] true vertical depth (TVD). The inclination angle was held at 58° to 1640 m [5,380 ft] MD and 1429 m [4,688 ft] TVD, where 340-mm [13ra-in.] casing was set. Drilling continued below the 340-mm [l3ra-in.] casing shoe, holding the inclination angle between 57 and 60° to 2830 m [9,285 ft] MD and 2054 m [6,739 ft] TVD, where 245-mm [9%-in.] casing was set. As will be explained later, continued drilling of the well required that sections of the steel drillstring be replaced with aluminum drillpipe. Thus, at the 245-mm [9%-in.] casing point, approximately 1372 m [4,500 ft] of 127-mm [5-in.] aluminum drillpipe was substituted for the steel pipe used earlier. The aluminum pipe was positioned immediately above the heavyweight drillpipe of the bottornhole assembly (BHA). The remainder of the drillstring above the aluminum drillpipe to surface was 127-mm [5-in.] steel drillpipe. Drilling continued below the 245-mm [9%-in.] casing shoe with the combined aluminum/steel drillstring, with the inclination angle held at about 59° to 3155 m [10,351 ft] MD and 2206 m [7,236 ft] TVD. At this point, an additional 457 m [1,500 ft] of steel drillpipe was removed from the drillstring and replaced with 127mm [5-in.] aluminum drillpipe in the same manner as described earlier. Drilling then continued at an inclination angle between 58 and 64° to the final total depth (TD) of 4007 m [13,145 ft] MD and 2635 m [8,645 ft] TVD. The total departure at this final TD was 2642 m [8,667 ft] from the surface location. The aluminum pipe used in this project was fitted with intemalflush, steel tool joints. 1 Approximately 250 joints (2286 m [7,500 ft]) of the aluminum drillpipe were obtained on a rental basis. Of these, 191 joints were new and 59 joints were used but in premium condition. The seamless drillpipe was specified as Alloy 2014-T6, with ...

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