NTERM (the number of potential surfaces involved: this should be 2
in this case). This parameter can not be changed
NPAR: number of lambda-doublet components included
If NPAR = 1, just = +1 states are included
If NPAR .ne. 1, both = +1 and = - 1 states are included
JMAX: maximum rotational quantum number
IGU: inversion symmetry of states included in expansion.
IGU = +1 for gerade states
IGU = -1 for ungerade states
for heteronuclear molecules IGU should be +1
ISA: Nuclear permutation symmetry (s/a label) of states
included in the expansion.
If the flag IHOMO is .TRUE.,
then only
s states will be included if ISA = +1 and only a states if
ISA = -1