
                  R O T I O N S

      ROTIONS calculates integrated cross-sections for rotational excitation
      of molecular ions. It takes input data from TMATRX, and a few parameters
      like the permanent dipole and/or quadrupole of the target (and rotational
      constant) are required to obtain the Coulomb-Born corresponding cross 
      sections.

      Input files:
        T-matrices                       (on unit LUTMTv )

      Output files:
        Cross section table              (on unit ixsout)

      The following PARAMETERs are used to define array dimensions

      MAXERN = 10     maximum number of energy subranges (defined in RSOLVE)
      MAXXCH = 1000   maximum number of scattering channels
      maxene = 10000  maximum number of energies to read
      maxnsym= 12     maximun number of molecular symmetries to read

      Namelist input /RXSECIN/

        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.
        
	anr_op   I   1         1     [0|1]
	   ! switch to activate the threshold correction to the cross 
	     sections. =0 do not apply the correction; =1 apply.	      

	aq       R   1         1.d-1 [0.:]
	   ! lower limit for the numerical integration of the quadrupole integrals M_02
	     and M_20. Some care should be taken with this number to be sure that the 
	     function to integrate do not extend to smaller values, but, at the 
	     same time, aq should not be "too" small because that produces
	     numerical error in the evaluation of the Coulomb functions by COULFG.
	     (This might change if an alternative subroutine to COULFG is found) 

	be       R   1         0.    [0.:]
	   ! rotational constant of the target (in cm-1)

	bq       R   1         2.d4  [0.:]
	   ! upper limit for the numerical integration of the quadrupole integrals M_02
	     and M_20. COULFG seems not to have problems in this case. In theory this value
	     should be infinite, but in practice is enough not to go too far. 
	     In fact, in doing so one avoids problems with numerical convergence
	     of the integral. 

	cb_op    I   1         0     [0|1]
	   ! switch to activate the calculation of Coulomb-Born cross sections.
	     =0 Only T-matrices are used to obtain rotational cross sections; 
             =1 T-matrix and CB rotational cross sections are obtained;
	     =2 Only CB rotational cross sections are obtained. cb_op=1,2 will only
	      work if the target is charged and \Delta j=1,2.

        EMIN     R   1         0.    [0.:MAXE]
           ! minimum required scattering energy (in units as specified by 
             IEUNIT).  MAXE is the maximum energy on the T-matrix file

        EMAX     R   1         MAXE  [0.:MAXE]
           ! maximum required scattering energy (MAXE is the maximum energy
             on the T-matrix file)

	GRID     I   1          1    [1|2]
	   ! Energy grid mode tu use when CB_OP=2. 1=linear, 2=logarithmic.

        IEUNIT   I   1          1    [1|2|3]  
           ! units in which input scattering energies are input
                 1= eV, 2=Hartree, 3= Ryd

	ION      I   1          1    [0:]
           ! charge of the target

        IPRNT    I   6          0    [0|1]
           ! Debug print switches :
             In each case -1 gives less than the default output and +1
             more than the default
                 (1) =1 Print all input data
                 (2) =1 Print vibrational wavefuction data
                 (3) =1 Debug output in dissociating channels
                 (4) =1,2,3 Debugging level for rotational CS calculations
                 (5) =1 not used
                 (6) =1 Print all output data

        ITFORM   C   1         'U'   ['U'|'F']
           ! Formatted/unformatted switch for unit LUTMT

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

        IXSN     I   1          1    [1:3]
           ! Units to be used for cross-section output
             1 = bohr**2
             2 = angstrom**2
             3 = pi*bohr**2

	ixsout   I   1          8    [1:]
	   ! logical unit for output of cross section table

	j        I   1          0    [0:]
	   ! initial rotational quantum number of the target

	jp       I   1          1    [0:]
	   ! final rotational quantum number of the target

	lmax     I   1          5    [0:30]
	   ! number of partial waves to add up to get the partial Coulomb-Born 
	     cross sections.
	     The total dipole CB CS is obtain "exactly" using a closure formula.

	lmaxq    I   1          20    [0;30]
	   ! number of partial waves to add up to get total quadrupole Coulomb-
	     Born cross sections. 

        LUTMTv   I   nsym       nsym*12    [1:]
           ! logical unit(s) holding input T-matrices

        MAXI     I   1          1    [1:NTARG]
           ! label of highest initial state for which cross-
             sections are required (here NTARG counts both electronic
             and vibrational states)

        MAXF     I   1         NTARG [1:NTARG]
           ! label of highest final state for which cross-sections
             are required (here NTARG counts both electronic and
             vibrational states)

        NAME     C   60                          
           ! title for any output

	mjj       I   1          6    [0:]
	   ! Maximum total angular momentum to be considered in obtaining 
	     the rotational T-matrices in the LAB-frame.

	nsym      I   1          1    [1:5]
	   ! number of molecular symmetries to include in the calculation

        NTSET     I   1          1    [0:]
           ! Set number for input T-matrices 

	numener   I   1          0    [0:maxene]
	   ! number of energies to be read from the T-matrix files (useful
	     if the T-matrices have been obtained for a lot of energies and
	     one is checking if the program works!)

	q1        R   1          0    [0:]
	   ! permanent dipole moment of the target in Debye

	q2        R   1          0    [0:]
	   ! permanent quadrupole moment of the target in atomic units 
