Parameters of the multiplet

When selecting the HFS method, you must give the name of a file that contains the relative positions and intensities of the components of your multiplet:
LAS> method hfs hfs-n2hp.dat
Relative intensities may be normalized or not. Here follow two examples, for the N$_2$H$^+$ multiplet.

  7               ! 1st line: Number of components
   6.9360  1.     ! 1st column: Velocity shift, for each component,
   5.9841  5.     !             (in km/s) with respect to the reference
   5.5452  3.     !             component you choose (here the 5th one).
   0.9560  5.     ! 2nd column: The relative strength of each component.
   0.0000  7.     !             Here, they are not normalized.
  -0.6109  3.     !
  -8.0064  3.     !

  7                  ! As before.
  14.9424 1./27.     ! The reference velocity is now that of the last
  13.9906 5./27.     ! component.
  13.5516 3./27.     ! The intensities are normalized (you could also
  8.9624  5./27.     ! put numerical values rather that fractions).
  8.0064  7./27.     !
  7.3955  3./27.     !
  0.      3./27.     !

Let us call and the positions and relative intensities of the $N$ components of the multiplet. We define $S=\sum\ensuremath{r_i}$. In the first case, we thus have $N=7$ and $S=27$.