Matrix isolation study of the reaction of f atoms with co infrared and ultraviolet spectrum of the free radical fco

Matrix isolation of reaction of fluorine atoms with carbon monoxide - infrared and ultraviolet spectrum of free radical fluorocarbon monoxid

FERMI RESONANCE IN SOLIDS

Author Institution: National Bureau of StandardsThe infrared absorption spectra of $CF_{4}$ and $CCl_{4}$ have been observed in both the pure form and in rare gas matrices at low temperatures. The region studied corresponded to the $\nu_{3}, 2\nu_{4}$ and $\nu_{3}, \nu_{1}+\nu_{4}$ Fermi doublets of $CF_{4}$ and $CCl_{4}$ respectively. The interaction of the vibrations in Fermi resonance in these molecules changes considerably from that found in the gaseous phase. The spectral features observed will be discussed and related to recent theories

VIBRATIONAL SPECTRA OF THE PHTHALONITRILES

Author Institution: National Bureau of StandardsSolid state spectra for samples of 1,2-, 1,3-, and 1,4--dicyanobezenes have been recorded in the 5000--260 $cm^{-1}$ region using prism-grating and prism spectromenters. Comparisons will be made with the spectra of other disubstituted benzenes in the long wavelength region. A detailed analysis of the vibrational spectra is being undertaken and some tentative assignments are suggested

LOW-FREQUENCY INFRARED SPECTRA OF BUTADIENE AND SOME DERIVATIVES

Author Institution: Molecular Spectroscopy Section, National Bureau of StandardsThe infrared spectra of 1,3 butadiene and several derivatives (including fluoroprene, isoprene, and chloroprene) have been investigated in the $250-600 cm^{-1}$ region in an effort to establish the low-frequency skeletal modes. The lowest in-plane fundamental in butadiene itself has been located at $303 cm^{-1}$; the analogous fundamental in the derivatives falls between 250 and $290 cm^{-1}$. The C-C single bond torsional fundamental in fluoroprene is found to be $156 cm^{-1}$ from the microwave spectrum, and probably has a similar frequency in the other compounds. The correlation of the other skeletal bending modes will be discussed. The $A_{u}$ fundamental of butadiene at $525 cm^{-1}$ shows well-resolved rotational structure which confirms the planar trans conformations of the molecule

INFRARED SPECTRUM OF DIFLUORAMINE

Author Institution: Molecular Spectroscopy Section, National Bureau of StandardsThe infrared spectrum of gaseous difluoramine, $HNF_{2}$, has been investigated over the range $250-4000 cm^{-1}$. The fundamental frequencies (in $cm^{-1}$), their assignment and band types are as follows: $3193, \nu_{1}(a^{\prime}$, type C); 1306, $\nu_{2}(a^{\prime}$, type B); 972, $\nu_{3}(a^{\prime}$, type B); $500, \nu_{4}(a^{\prime}$, type B); $1424, \nu_{5}(a^{\prime\prime}$, type A); $888, \nu_{6}(a^{\prime\prime}$, type A). the three type-B bands are well resolved into Q branches with a spacing of approximately $3 cm^{-1}$.The P and R branches of the type A $888 cm^{-1}$ band are also resolved with a spacing of approximately $0.7 cm^{-1}$. The values of the rotational constants A and ${^{1}}/_{2} (B+C)$ obtained from these infrared results are in agreement with those determined much more precisely from the microwave spectrum. No inversion splitting was detected in the fine-structure of the resolved bands

Experimental study of radiative heat transfer in a translucent fuel sample exposed to different spectral sources

Radiative heat transfer to a solid is a key mechanism in fire dynamics, and in-depth absorption is especially of importance for translucent fuels. The sample-heater interaction for radiative heat transfer is experimentally investigated in this study with two different heaters (electric resistance and tungsten lamp) using clear PolyMethylMethAcrylate (PMMA) samples from two different formulations (Plexiglass and Lucite). First, the significant effects of the heater type and operating temperature on the radiative heat transfer are revealed with broadband measurements of transmittance on samples of different thicknesses. Then, the attenuation coefficient in Beer-Lambert's law has been calculated from detailed spectral measurements over the full wavelength range encountered in real fires. The measurements present large spectral heterogeneity. These experimental results and calculation of in-depth absorption are used to explain the reason behind the apparent variation of the fuel absorbance with the sample thickness observed in past studies. The measurement of the spectral intensity emitted by the heaters verifies that the common assumption of blackbody behavior is correct for the electric resistance, whereas the tungsten lamp does not even behave as a greybody. This investigation proofs the necessity of a multi-band radiation model to calculate accurately the fire radiative heat transfer which affects directly the in-depth temperature profiles and hence the pyrolysis process for translucent fuel