Computing Lifetimes

The lifetimes are computed by summing Einstein A coefficients as

\(\tau_{i'}= \sum_{i''< i'} \frac{1}{A_{i',i''}}\)

For states with no channels to lower states, the lifetimes are considered undefined and assign NaN. This feature is based on the external library IEEE. In the older version of ExoCross, such states were assigned -1.0000.

Example of the input file for lifetimes:

lifetime

output 28SiO-16

States 28Si-16O__EBJT.states
Transitions 28Si-16O__EBJT.trans

By default, the lifetimes are written into the column 6 assuming that the uncertainty column is present which should be always stays as column 5. If however the uncertainties are not given and the lifetimes should be written into column, this option can be specified using the QN section:

QN
 lifetime 5
END

Lifetimes as input for line profiles

If pre-dissociation is considered, the lifetime can be used to estimate the effective line width. This option can be activated using the following input

predissociation

QN
 lifetime 5
END

For more details, see the “Line profiles” section.