The Hibridon code can determine energies and eigenvectors of weakly-bound states as well as scattering and photodissociation cross sections. This involves only a slight change in the methodology. To determine bound-state energies, set:

BOUNDC = .TRUE.

This will invoke a variational calculation of all bound-state levels using the distributed Gaussian method of I. P. Hamilton and J. C. Light [J. Chem. Phys. 84, 306 (1986)]. The R-dependence of the wavefunction will be expanded in a set of Gaussian functions:

$\chi_m(R) = e^{-\alpha(R-R_m)^2}$

This set of functions is defined by several of the Hibridon input parameters, as follows:

• R1: smallest value of R_m
• R2: largest value of R_m
• SPAC: spacing between successive values of R_m
• C: parameter which determines the exponential scale factor of the distributed Gaussian functions, with α=(C/SPAC)².
• EIGMIN: lower limit on the minimum allowed eigenvalue of the overlap matrix. If the minimum eigenvalue is less than this value, the parameter C should be increased.
• DELR, HSIMP: The matrix elements of W(R) are evaluated by a Simpson’s rule integration extending from R1–DELR to R2+DELR in steps of HSIMP.

Reasonable starting values for these parameters are (see the file bound_parameters for a detailed discussion of setting these parameters):

• SPAC: 0.4
• C: 0.5
• EIGMIN: 1.e-6
• DELR: 1
• DR: 0.1

If the flag CSFLAG is .TRUE., then a bound-state calculation will be carried out within the centrifugal decoupling approximation including only channels for which the projection of the total angular momentum along R is equal to

• NUMIN, (if FLAGHF = .FALSE.)
• NUMIN+0.5, (if FLAGHF = .TRUE.)

If BOUNDC = .FALSE. (the default), then a scattering or photodissociation calculation is performed.