- NAME
AIRTOVAC
- PURPOSE
Convert air wavelengths to vacuum wavelengths
- EXPLANATION
Wavelengths are corrected for the index of refraction of air under
standard conditions. Wavelength values below 2000 A will not be
altered. Uses relation of Ciddor (1996).
- CALLING SEQUENCE
AIRTOVAC, WAVE_AIR, [ WAVE_VAC]
- INPUT/OUTPUT
WAVE_AIR - Wavelength in Angstroms, scalar or vector
If this is the only parameter supplied, it will be updated on
output to contain double precision vacuum wavelength(s).
- OPTIONAL OUTPUT
WAVE_VAC - Vacuum wavelength in Angstroms, same number of elements as
WAVE_AIR, double precision
- EXAMPLE
If the air wavelength is W = 6056.125 (a Krypton line), then
AIRTOVAC, W yields an vacuum wavelength of W = 6057.8019
- METHOD
Formula from Ciddor 1996, Applied Optics 62, 958
- NOTES
Take care within 1 A of 2000 A. Wavelengths below 2000 A *in air* are
not altered.
- REVISION HISTORY
Written W. Landsman November 1991
Use Ciddor (1996) formula for better accuracy in the infrared
Added optional output vector, W Landsman Mar 2011
Iterate for better precision W.L./D. Schlegel Mar 2011