HITRAN on the Web

Guest   |  

Parameters of spectral lines

This section describes the parameters of spectral lines contained in the portal database. The symbolic notation of the parameters correspond to the symbolic notation used in the in the Linelist tab of Simulation results page and in lists of spectral lines that are downloaded to the user's computer.
Here is afull set of parameters. Most of data sources contain only some subsets of these parameters.
 

M: The molecular species identification number

The internal identifier of the molecule in the database. For molecules presented in HITRAN databank, it matches the ID of HITRAN (M=MH). For the molecules presented in GEISA databank, but missing in HITRAN, it is calculated according to the formula M=100+MG. For molecules that are missing in both HITRAN and GEISA databanks this number is more than 200.

I: The isotopologue identification number

The internal identifier of the isotopologue in the database according HITRAN rules: by decreasing of a natural terrestrial isotopic abundance. So,  I=1 for the most abundant isotopologue, I=2 for the next most abundant, etc.

WN: The wavenumber of the spectral line transition [cm-1] in vacuum

The transition between lower and upper states i and j is accompanied by the emission or absorption of a photon of energy WN = ΔE = Ei - Ej cm−1 (νij in HITRAN notation).

S: The spectral line intensity [cm/molecule] or [cm−1/(molecule·cm−2)]

The intensity is defined at Tref of current data source for a single molecule, per unit volume. The units in unreduced form are used in order to emphasize that the intensity can be thought of as wavenumbers per column density, as commonly used in atmospheric transmission and radiance codes.
Lists of spectral lines calculated in the system provide the user the value of this parameter at a temperature and a concentration specified in the conditions of the spectrum simulation.

El: The lower-state energy of the transition [cm-1]

This quantity has been defined such that the minimum possible level of the particular isotopologue is set to zero.

A: The Einstein A-coefficient for spontaneous emission [c-1]

This parameter is detailed described in [3] used in the studies of non-local thermodynamic equilibrium in the atmosphere, astrophysics, and fundamental physics.

Lenv: The environment-broadened half width for Lorentz profile [cm−1/atm]

This parameter is used to build Lorentz profile of the spectral line. It represents the the half width of a spectral line at the half-maximum of the probability at temperature Tref of current data source, and at pressure Pref = 1 atm. In the case of the terrestial atmosphere the air-broadened half width is used as Lenv ( γair in HITRAN notation).
Lists of spectral lines calculated in the system provide the user the value of this parameter at a temperature and a pressure specified in the conditions of the spectrum simulation.

Lself: The self-broadened half width for Lorentz profile [cm−1/atm]

This parameter is used to build Lorentz profile of the spectral line. It represents the the half width of a spectral line at the half-maximum of the probability at temperature Tref of current data source, and at pressure Pref = 1 atm ( γself in HITRAN notation).
Lists of spectral lines calculated in the system provide the user the value of this parameter at a temperature and a pressure specified in the conditions of the spectrum simulation.

Nt: The temperature-dependence exponent for Lenv and Lself

This parameter is used to change the value of the Lorentz halfwidth of the spectral line in dependence on temperature. In more detail this dependence is described in the section Dependence on temperature and pressure.

Pshift: The pressure shift of the line position [cm-1]

The pressure shift of the transition wavenumber leads to a shifted position of the line.
In fact, the shift values are available in HITRAN data source only, the availability of shift values is still sparse, and the experimental values have high uncertainties associated with them.

GQNup, GQNlow: The sets of "global" quantum number for upper and lower vibrational states

The set of values of quantum numbers that uniquely identifies the upper and lower vibrational states of the transition.

LQNup, LQNlow: The sets of "local" quantum number for upper and lower rotational states

The set of values of quantum numbers that uniquely identifies the upper and lower rotational states of the transition.

Swup, SWlow: The upper and lower state statistical weights

The statistical weight includes electronic, vibrational, rotational, and nuclear statistics; caution must be exercised when calculating weights for degenerate states. These parameters are explained in Šimečková et al.[1].

Ierr: Uncertainty indices (in HITRAN only)

Iref: Reference indices (in HITRAN only)

References

  1. M. Šimečková, D. Jacquemart, L. S. Rothman, R. R. Gamache, and A. Goldman, "Einstein A-coefficients and statistical weights for molecular absorption transitions in the HITRAN database", J. Quant. Spectrosc. Radiat. Transfer 98, 130-155 (2006).