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# AIRVAC -- Convert dispersion coordinates to air or vacuum values.
# The index of refraction formulas used are from Allen's Astrophysical
# Quantities (1973).
#
# This task takes in a file of wavelengths in Angstroms and converts between
# air and vacuum to an output file of wavelengths in Angstroms. It will
# pass any comments and data after the first wavelength column to the
# output.
#
# To install and use copy the script to your IRAF home directory with the
# name airvac.cl. Then interactively (for use during the current IRAF session)
# or in your loginuser.cl (for use during future IRAF sessions) enter
# "task airvac=home$airvac.cl".
procedure airvac (input, output)
file input {prompt="Input file of wavelengths in Angstroms"}
file output {prompt="Output file of wavelengths in Angstroms"}
string type = "air2vac" {prompt="Conversion (air2vac|vac2air)",
enum = "air2vac|vac2air"}
real t = 15. {prompt="Temperature (C)"}
real p = 760. {prompt="Pressure (mmHg)"}
real f = 4. {prompt="Water vapour pressure (mmHg)"}
struct *inlist
begin
file in, out
struct label
int n
real a, b, w
in = input
out = output
printf ("# airvac (%s, %s, type=%s, t=%.6g, p=%.6g, f=%.6g)\n",
in, out, type, t, p, f, > out)
inlist = input
while (fscan (inlist, line) != EOF) {
n = fscan (line, w, label)
if (n == 0) {
print (line, >> out)
next
}
b = (10000. / w) ** 2
a = 64.328 + 29498.1 / (146 - b) + 255.4 / (41 - b)
a = a * p * (1 + (1.049 - 0.0157 * t) * 1e-6 * p) /
(720.883 * (1 + 0.003661 * t))
a = a - (0.0624 - 0.000680 * b) / (1 + 0.003661 * t) * f
a = 1 + a / 1e6
if (type == "air2vac")
w = a * w
else if (type == "vac2air")
w = w / a
print (w, label, >> out)
}
inlist = ""
end
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