                   I N T E R V (diatomic codes only)

      INTERV is an optional module which reorders scattering channels defined
      by either INTERF or VIBRMT.  It should be called immediately before
      RSOLVE.  Reordering is needed if the scattering channels are not
      in order of increasing energy.  This can happen if target curves of
      different symmetry cross or if vibrational levels of more than one
      electronic state are treated non-adiabatically.

      Input files:
        Channel and target data          (on unit LICHAN)
        R-matrix data                    (on unit LIRMT )

      Output files:
        Channel and target data          (on unit LOCHAN)
        R-matrix data                    (on unit LORMT )


      The following PARAMETERs are used to define array dimensions

      MAXNC  = 1000 maximum number of scattering channels
      MAXTGT = 100  maximum number of target electronic states
      MAXPOL = 200  maximum number of non-adiabatic R-matrix poles
      MAXPTS = 30   maximum number of geometries

      Namelist input /INTVIN/

        The format of the following is 
       (Name, Type, Dimension, Default, Limits, ! description)
        Unless specified otherwise, the default value applies to all elements
        of array variables.
        
        ICFORM   C   1         'U'   ['U'|'F']
           ! format flag for channel dataset, 'F' for formatted, 'U' for
             unformatted

        IPRNT    I   6          0    [-1,0,1]
           ! Debug print switches :
                 (1) exact copy of input data
                 (6) exact copy of output data

        IRFORM   C   1         'U'   ('U'|'F')
           ! format flag for R-matrix dataset, 'F' for formatted, 'U' for
             unformatted

        ITGORD   I   MAXTGT*MAXPTS
           !  array which defines the required reordering.  The format is
              NGEOM sets of NTARG integers each of which specifies the 
              ordering at the particular geometry.  The equilibrium
              geometry will usually be in normal order (1,2,3,4...)

        IWRITE   I   1          6    [1:]        
           ! logical unit for printed output

        LICHAN   I   1         10    [1:]        
           ! logical unit for input channel and target dataset

        LIRMT    I   1         21    [1:]
           ! logical unit holding input R-matrix poles, amplitudes etc.

        LOCHAN   I   1         11    [1:]        
           ! logical unit for output channel and target dataset

        LORMT    I   1         22    [1:]
           ! logical unit holding output R-matrix poles, amplitudes etc.

        NAME     C   60                          
           ! title for any output

        NCHSET    I   1          1   [1:]        
           ! set numbers of channel datasets

        NRMSET    I   1          1   [1:]
           ! set numbers of R-matrix datasets

        NGEOM    I   1           1   [1:]        
           ! number of geometries for which data is to be reordered

        R        R   1               [0.:]        
           ! internuclear separations

        TYPE     C   1           I   [I,V]        
           ! type of input data, I from INTERF, V from VIBRMT
