Rayleigh scattering cross sections of combustion species at 266, 355, and 532 nm for thermometry applications

Rayleigh scattering cross sections are measured for nine combustion species (Ar, N2, O2, CO2, CO, H2, H2O, CH4, and C3H8) at wavelengths of 266, 355, and 532 nm and at temperatures ranging from 295 to 1525 K. Experimental results show that, as laser wavelengths become shorter, polarization effects become important and the depolarization ratio of the combustion species must be accounted for in the calculation of the Rayleigh scattering cross section. Temperature effects on the scattering cross section are also measured. Only a small temperature dependence is measured for cross sections at 355 nm, resulting in a 2-8% increase in cross section at temperatures of 1500 K. This temperature dependence increases slightly for measurements at 266 nm, resulting in a 5-11% increase in cross sections at temperatures of 1450 K.     

Reinvestigation of far-infrared laser emissions from hydrazine and deuterated isotopes of difluoromethane and methanol

Hydrazine (N₂H₄) and the deuterated isotopes of difluoromethane (CD₂F₂) and methanol (CH₃OD and CD₃OH) have been reinvestigated as sources of far-infrared (FIR) laser emissions using an optically pumped molecular laser system designed for wavelengths below 150 microns. With this system, seven FIR laser emissions from optically pumped N₂H₄, CH₃OD and CD₃OH were discovered with wavelengths ranging from 54.0 to 185.0 m. In addition, the polarizations of eight previously observed laser emissions from optically pumped N₂H₄, CH₃OD and CD₂F₂ were measured for the first time. All laser emissions are reported with their operating pressures, relative polarizations and wavelengths, measured to ±0.5 m. The effectiveness of this particular system in generating short-wavelength laser emissions has been further demonstrated by the improvement in output power observed from nine known FIR laser emissions. PACS 07.57.Hm; 42.55.Lt     

Development of chiral HPLC for selenoamino acids with ICP-MS detection:application to selenium nutritional supplements

The enantiomeric separation of three underivatized seleno-amino acids, D,L-selenocystine, and D,L-selenomethionine, and D,L-selenomethionine, with UV and ICP-MS detection is described. An HPLC column with a chiral crown ether stationary phase and a mobile phase of 0.10 M HCIO4 was used. Absolute detection limits obtained with UV detection ranged from 34.5 to 47.1 ng whereas those obtained with the plasma detector were ca. 40-400 times better. The separations with either detector were good, with the little detector effect on the resolution. Ten commercially available dietary selenium supplements were analyzed using the chiral column to identify and quantify the selenium species present with both detection modes. Selenium species were easily identified using ICP-MS detection, whereas UV detection was not viable because of interferences from the sample matrix and inadequate sensitivity. Selenium species that were unretained using the chiral column were identified using anion exchange chromatography. Total amounts in the samples were also measured using a conventional digestion and enzymatic digestion with ICP-MS detection.