ATOMIC_HYDROGEN    (1.0)        /* H   */ (-)
MOLECULAR_HYDROGEN (2.0)        /* H2  */ (21.01-32.27)
HELIUM             (4.0)        /* He  */ (-)
ATOMIC_NITROGEN    (14.0)       /* N   */ (-)
ATOMIC_OXYGEN      (16.0)       /* O   */ (-)
METHANE            (16.0)       /* CH4 */ (90.99-190.5)
AMMONIA            (17.0)       /* NH3 */ (164.0-371.4)
WATER_VAPOR        (18.0)       /* H2O */ (273.-573.)
NEON               (20.2)       /* Ne  */ (15.8-27.)
MOLECULAR_NITROGEN (28.0)       /* N2  */ (63.14-126.)
CARBON_MONOXIDE    (28.0)       /* CO  */ (-)
-NITRIC_OXIDE      (30.0)       /* NO  */ (-)
MOLECULAR_OXYGEN   (32.0)       /* O2  */ (54.36-154.33)
HYDROGEN_SULPHIDE  (34.1)       /* H2S */ (138.8-349.4)
ARGON              (39.9)       /* Ar  */ (83.78-150.72)
CARBON_DIOXIDE     (44.0)       /* CO2 */ (154.26-195.89)
NITROUS_OXIDE      (44.0)       /* N2O */ (129.7-187.6)
NITROGEN_DIOXIDE   (46.0)       /* NO2 */ (217.5-294.)
OZONE              (48.0)       /* O3  */ (92.7-162.0)
SULPHUR_DIOXIDE    (64.1)       /* SO2 */ (177.6-414.8)
SULPHUR_TRIOXIDE   (80.1)       /* SO3 */ (333.-483.)
KRYPTON            (83.8)       /* Kr  */ (72.21-208.)
XENON              (131.3)      /* Xe  */ (161.70-184.70)

ATOMIC_HYDROGEN, MOLECULAR_HYDROGEN, HELIUM, ATOMIC_NITROGEN, 
ATOMIC_OXYGEN, METHANE, AMMONIA, WATER_VAPOR, NEON, MOLECULAR_NITROGEN, 
CARBON_MONOXIDE, NITRIC_OXIDE, MOLECULAR_OXYGEN, HYDROGEN_SULPHIDE, 
ARGON, CARBON_DIOXIDE, NITROUS_OXIDE, NITROGEN_DIOXIDE, OZONE, 
SULPHUR_DIOXIDE, SULPHUR_TRIOXIDE, KRYPTON, XENON

H, H2, He, N, O, CH4, NH3, H2O, Ne, N2, CO, NO, O2, H2S, 
Ar, CO2, N2O, NO2, O3, SO2, SO3, Kr, Xe

http://webbook.nist.gov/chemistry/form-ser.htm