Basis Subroutine and System Specific Parameters: Collision of a Symmetric Top with a Linear Molecule in a ¹Σ State

System subroutine: systpln

Basis subroutine: hibastpln.f

A Symmetric top and a Linear Molecule in a ¹&Sigma State
Ref. C. Rist, M. H. Alexander, and P. Valiron, J. Chem. Phys. 98, 4662 (1993).

NTERM (the number of potential surfaces involved: this should be 2 in this case). This parameter can not be changed

NUMPOT: an index representing the particular potential used. This variable is passed to the POT subroutine

IPOTSY: cylindrical symmetry of potential. If the flag IHOMO = .true., only terms with mu₁ equal to an integer multiple of IPOTSY can be included in the potential. Example: for NH₃, IPOTSY = 3

IOP: ortho/para label for molecular states of symmetric top. If IHOMO =.true. then

if IOP = 1: only para states included in channel expansion
if IOP = -1: only ortho states included in channel expansion

NINV: number of inversion doublets included

if NINV = +1, only + inversion levels included
if NINV = -1, only - inversion levels included
if NINV = 2, both inversion levels included

KMAX: the maximum projection quantum number included

JMAX0: the maximum rotational angular momenta for the k = 0 stack

JMAX1: the maximum rotational angular momenta for the k = 1 stack

JMAX2: the maximum rotational angular momenta for the k = 2 stack

JMAX3: the maximum rotational angular momenta for the k = 3 stack

JMAX4: the maximum rotational angular momenta for the k = 4 stack

JMAX5: the maximum rotational angular momenta for the k = 5 stack

JMAX6: the maximum rotational angular momenta for the k = 6 stack

IPOTSY2: symmetry of potential. if the linear molecule is homonuclear then IPOTSY = 2 and only terms with lambda₂ even can be included in the potential, else IPOTSY = 1

J2MAX: the maximum rotational angular momentum for the linear molecule

J2MIN: the minimum rotational angular momentum for the linear molecule

BROT, CROT: rotational constants of symmetric top
DROT: rotational constant of diatomic molecule

E(jkj₂) = BROT j (j + 1) + (CROT - BROT) k² + DROT j₂ (j₂ + 1)