spectrum.c takes vibrational frequencies and intensities and
plots a realisticlooking spectrum. It is written in strict ANSI
C and should compile painlessly with
cc spectrum.c o spectrum lm
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Paul Soper All the usual disclaimers apply
DuPont Central Research soperpd@esvax.dnet.dupont.com
P.O. Box 80328 Tel (302)6951757
Wilmington, DE 198800328 FAX (302)6952112

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This program takes a set of transtion frequencies and
intensities and produces a data set suitable for plotting. By
choosing a reasonable valueof HWHM you can create a
realisticlooking specturm.
The input file should have one transition frequency and
intensity per line.
i Input file name of transition frequencies and intensities
o Output file of a plottable spectrum
[l] Lineshape
0 (Lorentzian),
1 (Gaussian),
or 2 (Delta function  default)
[h] HWHM (HalfWidth at HalfMaximum). Ignored if the
lineshape is the delta function
[sc] Frequency scale factor. Multiply all input frequencies
by this value. (does not scale HWHM)
[sf] Starting frequency of the output file
[ef] Ending frequency
[fs] Frequency step size. Ignored if the lineshape
is the delta function
[d] Sort output by decreasing frequency
(default is by increasing frequency)
[n] Normalize intensities to 100
[nf] Normalization factor. Divide all output intensities
by this value.
[wnf] Write the normalization factor to a file. (This allows
a factor to be shared among spectra for consistent
normalization.) The name of the file is that of the
output file with \".nf\" appended.
[w] After generating the spectrum from frequencies in wavenumbers,
write the ouput file with wavelengths in nanometers.
Quantum mechanics programs such as Gaussian 92, DGAUSS, MNDO91, and MOPAC
can calculate vibrational and other transition frequencies. However, these
are given as (frequency, intensity) pairs. They have no width and cannot
even be plotted directly as a delta function. This program takes those data
and creates a more realistic spectrum which is suitable for plotting.
The input file should have one frequency and one intensity per line,
separated by whitespace (spaces or tabs). The output file has the same
format.
This program uses only functions included in the ANSI C specification.
Paul D. Soper
DuPont
Central Research & Development
E328/123
DUCOM 6951757
