Thermopower of doped semiconducting hydrogenated amorphous carbon films

The thermopower S(T) and electrical conductivity have been measured from 25 to 250C for semiconducting a-C:H films doped with boron or phosphorus. S has the expected sign (positive for B-doping and negative for P-doping), is low for all films (10–50 μ V/K), and increases nearly linearly with T. This behavior, along with that observed for the electrical conductivity, is consistent with conduction via hopping at or near the Fermi level which has been shifted via doping from near mid-gap into broad bands of tail states at the appropriate band edges.     

Organic ions in the gas phase—XXIII: Loss of CH3 from polymethylbenzenes

The mass spectra of a series of deuteriated polymethylbenzenes confirm and extend the model derived from labeled p-xylenes for the loss of a methyl radical under electron impact. A methyl group flanked by two methyls undergoes no exchange before being lost. But one adjacent to an unsubstituted position appears to exchange with the o-hydrogen atom via a methyl-methylene-methyl cycle. At least in p-xylene, reformation of the methyl group may well be concerted with its loss. A similarly concerted coupling of CH₂ and H and loss of the resultant methyl group could account for an apparent inconsistency between the mass spectra of methyl alkyl and phenyl alkyl ketones.     

Homogeneous chemical vapor deposition of amorphous semiconductor thin films

In this paper we discuss the properties of amorphous hydrogenated silicon and germanium films prepared by homogeneous chemical vapor deposition. Emphasis is placed upon the important differences between HOMOCVD and plasma-deposited films. Experiments and calculations are presented which illustrate the most important reactor dynamical parameters.     

A theorem on accepted elasticity in certain local arithmetical congruence monoids

We give necessary and sufficient conditions for a certain class of local arithmetical congruence monoids (or ACMs) to have accepted elasticity.     

Mass spectrometry of 1 phenyl-1, 2-dibromopropylphosphonic acid and its methyl ester

$\text{erythro}$-1-Phenyl-1,2-dibromopropylphosphonic acid is known to decompose rapidly into the monomeric metaphospbate-anion (PO₃), 1-phenyl-1-bromopropene, and bromide ion in protic or aprotic solvents in the presence of a hindered tertiary amine. The present study compares the behavior of this phosphonic acid in solution and in the gas phase. The gas-phase thermolysis of the acid involves mainly the loss of bromine and of the phosphoryl group, -P(O)(OR) (OR') (R = R' = H). The same type of pathway is followed in the ionization/excitation processes (“cationic reactions”) that follow from electron impact in mass spectrometry. The thermal and cationic reactions of the monomethyl and dimethyl esters of the phosphoric acids (R=H,R'= CH₃ and R = R' = CH₃, respectively, in -P(O)(OR)(OR')) are entirely analogous to those of the free dibasic acid.     

The structure and mechanism of formation of C5H9O+ from ionized phytyl methyl ether

The recent proposal that ionized phytyl methyl ether [C₁₆H₃₃(CH₃)C=CHCH₂OCH ₃ ^+· ] undergoes an allylic rearrangement to ionized isophytyl methyl ether [CH₂=CHC(C₁₆H₃₃)(CH₃)OCH ₃ ^+· ] before elimination of an alkyl radical is discussed. Both literature precedent and new results in which the structure of the [M-C₁₆H ₃₃ ^· ]⁺ fragment ion is established by comparison of its collision-induced dissociation mass spectrum with the spectra of isomeric C₅H₉O⁺ ions of known structure are inconsistent with this proposal. The forma Hon of CH₃CH=CHCH=O⁺CH₃ by loss of a γ-alkyl substituent without skeletal isomerization rather than CH₂=CHC(CH₃)=O⁺CH₃ after allylic rearrangement is explained in terms of a mechanism that involves two 1,2-H shifts, followed by σ-cleavage of the resultant ionized enol ether, C₁₆H₃₃(CH₃)CH-CH=CHOCH ₃ ^+· .     

Reminiscences of the early days of mass spectrometry in the petroleum industry

This retrospect traces the development of commercial mass spectrometers for use in the petroleum industry, starting with the formation of Consolidated Engineering Corporation in 1937 and installation of their first instruments in 1942 and 1943. During the middle and late forties, just keeping the machines running placed major demands on the time, energy and ingenuity of mass spectrometrists. The fifties saw progressive exploration of the chemical basis of mass spectra, culminating in the Eighth Annual Meeting of ASTM Committee E-14 on Mass Spectrometry in 1960. This meeting marked a turning point in the development of the field—its transformation from what was originally almost a cult to a widely accepted and recognized branch of physical organic chemistry.     

The nominal butyl ester ion in the mass spectra of long-chain n-alkyl esters: A postscript

n-Octadecyl benzoate, taken as a model for long-chain n-alkyl carboxylates generally, loses C₁₄H₂₈ under electron impact to yield a product with the same elemental composition as the butyl benzoate molecular ion. This product retains quantitatively one hydrogen from C-6, and seems to be formed as an oxygen-protonated 4-benzoyloxybutyl radical. It reacts further to lose H₂O, in which deuterium labeling demostrates that the second hydrogen atom comes predominantly from C-4. The intermediate reorganization, for which the driving force is presumably furnished by the instability associated with a primary radical, is pictured in terms of cyclization via bonding between the C-4 radical site and the benzoyl carbon concerted with hydrogen migration via a 4-membered quasicyclic transition state.