COMPACT TABLE FOR THE PUBLICATION OF INFRARED-SPECTRA THAT ARE QUANTITATIVE ON BOTH INTENSITY AND WAVE-NUMBER AXES

A Compact Table format is presented for the publication of infrared sp ectra that are quantitative on both intensity and wavenumber axes. The format is illustrated with a molar absorption coefficient spectrum, E (m)(nu) vs. nu, and with infrared real and imaginary refractive index spectra, n(nu) vs. nu and k(nu) vs. nu, respectively. The algorithm co nsists of two steps: first, the number of spectral points is reduced b y using larger wavenumber spacings than appear in the original spectru m; second, the resulting spectral points are presented in a compressed table format. The Compact Table is about one tenth the size required for the original spectrum to be presented in a conventional XY table. The essential criterion for increasing the wavenumber spacing is that it must be possible to recover the original spectrum by interpolation to an accuracy better than that of the original spectrum. Nearly all t he recovered imaginary refractive index and molar absorption coefficie nt values are within 1% of the original values, and for each quantity the average of the magnitudes of the accuracies of recovery is 0.2%. T he real refractive index spectrum is most accurately recovered by Kram ers-Kronig transformation of the recovered imaginary refractive index spectrum. Nearly all the recovered real refractive index values are wi thin 0.02% of the original values, and the average of the magnitudes o f the accuracies of recovery is 0.005%. The real and imaginary infrare d dielectric constant spectra, epsilon'(nu) vs. nu and epsilon''(nu) v s. nu, can be calculated from the recovered data with an accuracy in e psilon' that is about one half of that of the real refractive index an d an accuracy in epsilon'' that is approximately that of the imaginary refractive index. The detailed method is outlined and is applied to i nfrared intensities of chlorobenzene. Computer programs are presented for the construction of the Compact Table and for the recovery of the full spectrum from the tabulated information.