A calibration system has been developed to provide increased accuracy in the measurement of the irradiance responsivity appropriate for UV meters used with broadband, extended sources of the type employed in phototherapy. The single wavelength responsivity of the test meter is obtained in the wavelength range 250-400 nm by intercomparison with a transfer standard meter in a narrow, monochromatic beam. Traceability to primary standard irradiance scales is provided via the National Measurement System with a best uncertainty of 7% (at 95% confidence). The effective responsivity of the test meter, when used with broadband extended sources, is calculated using the measured spectral and angular response of the meter and tabulated data on the spectral and spatial characteristics of the source radiance. The uncertainty in the effective responsivity, independent of the source variability, is estimated to be 10% (at 95% confidence). The advantages of this calibration system over existing approaches are discussed.
The infrared spectra of B2Cl4 have been studied from 4000 to 33 cm−1 in the gaseous and crystalline states. The Raman spectra have been studied to 45 cm−1 in the liquid phase at several temperatures between − 30 and − 190°C, the sample being in a supercooled liquid or glassy state in the latter cases, and in the crystalline state after annealing. An assignment of the normal vibrations of the molecule in the planar form is given, and the frequency of the expected torsional mode has been calculated. Splitting of the modes resulting from the natural isotopic ratios of boron have been observed, especially in the higher-frequency modes. Evidence is presented that the conversion from the nonplanar D2d form in the liquid to the planar D2h form in the solid results from a greater lattice stabilization for the D2h form rather than a greater inherent thermodynamic stability of the planar form.
The ir spectra of 89 saturated aliphatic-branched and straight-chain esters are reported for the region 350–50 cm−1 and empirical correlations of the band frequencies are classified by the alcohol component. It is found that there is no consistent series of bands for all samples studied but within the individual classes, several discrete areas of absorption are specified. This verified that these vibrations are more sensitive to structural differences than the higher-frequency characteristic group frequencies and are more specific in the total identification of a given, sample.
The infrared spectra of B2Br4 have been studied from 4000 to 33 cm−1 in the gaseous and crystalline states. The Raman spectra of the liquid at low temperatures and of the crystalline solid have been studied to 30 and 40 cm−1, respectively. Eleven of the twelve vibrational modes have been assigned whereas the low-lying torsional mode is calculated to be between 15 and 20 cm−1. Based on the vibrational analysis, it is concluded that the staggered D2d conformation is maintained in both the fluid and crystalline states. This behavior is contrary to what has been observed for both the B2F4 and B2Cl4 molecules. It is concluded that the increased steric interactions which would occur in the planar form preclude this conformation for the bromide.
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