The temperature dependence of the half widths of some self-and foreign-gas-broadened lines of methane

The temperature dependence of the half width of four lines of the 2v₃ band of methane has been measured. The broadeners used were H₂, He, N₂, and CH₄. The temperature coefficients, defined by the relation $\text{γ = γ}{}_0\text{(}\text{T}\text{T}{}_0\text{)}{}^{\mathrm{n}}$, have been determined for all of the broadeners and, in some cases, depart significantly from a kinetic theory value of -0.5. Where possible, the half-widths were determined by two independent methods. All measurements were made at pressures below 2 atm absolute to reduce interfering effects from the wings of neighboring lines.     

The mass spectrometry of 2-methylthio(glyco)oxazoline derivatives of pentoses and hexoses

The fragmentation of 2-methylthio(glyco)oxazolines under electron impact has been investigated by low- and high-resolution mass spectrometry. Field desorption was used in those cases where the molecular ion was weak or missing. Fragmentation pathways were determined by monitoring metastable transitions and through the use of labeled compounds. The results support the anticipated structure for these compounds and show the sensitivity of the mass spectra toward ring size.     

Measurement of water by oven evaporation using a novel oven design.

Using an automated oven evaporation technique combined with the coulometric Karl Fischer method, the mass fraction of water has been measured in cement, coal, and refined oil samples. The accuracy of this method was established by using SRM 2890, water-saturated 1-octanol that was added to white oil. The samples were analyzed for total reactive Karl Fischer reagent (KFR) material, for interfering materials, and for material that does not react with the aldehyde–ketone KFR. All of the samples yielded volatile material that reacted with the standard KFR. None of the samples contained significant masses of material that reacted with iodine. The cement and coal SRMs contained no material that reacted with methanol and very little material that did not volatilize at 107°C. The refined oils contained some material that was volatile at 107°C and some at 160°C. However, none of this material reacted with the aldehyde–ketone reagent. These results show that the material in the solid samples is water and that the material in the refined oils is a material other than water which reacts with methanol to form water.     

Absolute frequency measurement of a 1.5-microm acetylene standard by use of a combined frequency chain and femtosecond comb

We have developed and characterized a pair of Doppler-free acetylene-stabilized diode laser frequency standards as optical communications references. The Allan deviation sigma/f of an individual system reaches a minimum of 4 x 10(-14) at a sampling time of 5000 s, and the long-term lock-point repeatability is found to be 0.4 kHz (one standard uncertainty), corresponding to a fractional uncertainty of 2 x 10(-12). Using a combination of a frequency chain and a self-referenced femtosecond comb, we have measured the frequency of line P(16) of the v1 + v3 overtone band of 13C2H2 to be 194,369,569,385.9 (3.0) kHz. The uncertainty of this number is limited solely by the reproducibility of the standards.