Water-vapor continuum CO2 laser absorption spectra between 27 degrees C and -10 degrees C.

Water continuum CO2 laser absorption spectra are reported for temperatures between 27 and -10 degrees C. The continuum is found to possess a negative temperature coefficient. The results obtained suggest that the magnitude of this temperature coefficient increases with increasing water pressure and decreasing temperature. The temperature coefficients between 27 and 10 degrees C for air mixtures containing 3.0- and 7.5-Torr water vapor are -2.0 +/- 0.4 and -2.9 +/- 0.5%/ degrees C, respectively. For mixtures with 3.0-Torr water the 10-0 degrees C temperature coefficient is -7.7 +/- 0.2%/degrees C. The temperature and water pressure dependencies observed for the continuum suggest that while both collisional broadening and water dimer mechanisms contribute to the continuum, the dimer mechanism is more important over this temperature range.

Carbon dioxide laser absorption spectra of toxic industrial compounds.

CO(2) laser absorption cross-section data are reported for acrolein, styrene, ethyl acrylate, trichloroethylene, vinyl bromide, and vinylidene chloride. These data indicate that sub parts per billion level, interference-free detection limits should be possible for these compounds by the CO(2) laser photoacoustic technique. Photoacoustic detectabilities below 40 ppb should be possible for these compounds in the presence of ambient air concentrations of water vapor and other anticipated interferences. These compounds are also found not to be important interferences in the detection of toxic hydrazine-based rocket fuels by CO(2) laser spectroscopic techniques.

Use of photoluminescence to investigate apparent suicides by firearms.

A photoluminescence technique, which detects lead and antimony in gunshot residue, was evaluated for use in investigations of apparent gunshot suicides. The study was conducted in conjunction with forensic science laboratories in five U.S. cities. Samples were collected by the adhesive lift method from the backs of the hands of 67 gunshot suicide victims, 41 subjects who died of other causes, and 31 live subjects with high occupational exposure to lead and antimony. Tentative simultaneous threshold levels of 0.85 microgram for lead and 0.01 microgram for antimony were selected as criteria for presuming the presence of gunshot residue on samples from the hands of these suicide victims. Although blood decreases the detectability of lead and antimony in the samples, 48% of the suicide cases involving handguns other than .22 revolvers exceeded the threshold levels for both lead and antimony. Methods are suggested for eliminating the effects of blood, which should significantly increase the success rate for cases involving these guns. A much lower success rate was obtained for cases involving .22 revolvers and long guns, as expected from the sparse amounts of residue found in previous test firings of these guns.

Carbon dioxide laser absorption spectra and low ppb photoacoustic detection of hydrazine fuels.

Absorption cross-section data are reported for the toxic rocket fuels hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine (UDMH), as well as for their selected air oxidation products dimethylamine, trimethylamine, and methanol at up to seventy-eight CO(2) laser wavelengths each. These data are important for the assessment of the capability of CO(2) laser-based spectroscopic techniques for monitoring low levels of hydrazine-fuel vapors in the ambient air. Interference-free detection sensitivities of <30 ppb have been demonstrated for UDMH using a laboratory photoacoustic detection system.

Investigation of the composition and formation constant of molecular complexes.

It has been the purpose of the present paper to investigate and explore the conditions under which the linear relation between Delta/C(D) (0) and Delta in the Hanna-Ashbaugh-Foster-Fyfe equation for the evaluation of equilibrium constants holds, (C(D) (0) is initial concentration of a donor and Delta is the observed chemical shift relative to the chemical shift of the acceptor) to obtain the equation representing the exact linear relation between Delta/C(D) (0) and Delta, when the linear relation between Delta/C(D) (0) and Delta holds, and to discuss how to use the Job method in nuclear magnetic resonance measurements to determine the stoichiometry of molecular complexes. We have found that the conventional belief that C(D) (0) should always be chosen to be much greater than C(A) (0) (initial concentration of acceptor) is not necessarily always true and the exact linear relation between Delta/C(D) (0) and Delta is represented by the equation Delta/C(D) (0) = K(1)Delta(0)/(1 + K(1)C(A) (0)) - K(1)Delta/(1 + K(1)C(A) (0))(2), where K(1) is the formation constant of the complex. It is shown that in the Job method of nuclear magnetic resonance measurements one has to plot DeltaC(A) (0) against the mole fraction, and the mole fraction at the maximum should give us the composition of the complex. Theoretical results have been verified experimentally on the weak interaction between naphthalene and methyl iodide.