(1) no2_uv00_238_666.dat  
    Converted from the HITRAN2008 database. (2011/01/22)

(2) o3abs_brion_195_660_vacfinal.dat
    Obtained from Kelley Chance. (2010/12/28)

(3) O2-O2_UV04.alt 
    Copied from HITRAN2008 UV Cross section data

(3a)O2-O2: O4_294K_BISA.dat
    The 294 K BISA measurements, converted to vacuum nm and with negative
    values set to 0.
    O4_294K_BISA_666.dat: removed zero points from both beginning and end