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How to use ERHAM with AABS (updated Feb2018 for use with R3 of ERHAM):
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This procedure has been considerably simplified relative to 
the previous version.  

In summary:

1/ For a generic name MOLNAM associated with the project first prepare 
   a) starting MOLNAM.CAT file with predictions
   b) stub MOLNAM.LIN  file in the same quantisation
   c) ERHAM input file MOLNAM.IN (perhaps by reusing some previous ERHAM
      input file and running step 5)

2/ Declare MOLNAM.LIN as the fitting file in SVIEW_L, load the spectrum
   into SVIEW_L and the .LIN file into ASCP_L
   
 -> 3/ Make measurements in the usual way, which will be appended to 
|      MOLNAM.LIN
|   
|   4/ Run LINERH to convert MOLNAM.LIN file to ERHAM input MOLNAM.IN
|   
|   5/ Run ERHAMZ_R3 (and edit MOLNAM.IN further as required by the fit)
|      This will also update MOLNAM.CAT.
|   
|   6/ If necessary, run ERHRES to update MOLNAM.LIN (and also generate 
|      a more compact, reformatted MOLNAM.RES file of results of fit)
|   
|_  7/ Refresh the .CAT and .LIN files in ASCP_L (ESC key) and loop back
       to step 3



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In more detail:
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All AABS project files have to be in the same directory: spectrum, fitting file,
predictions file(s), and SVIEW_L.INP.  

It is often more convenient to keep the files associated with ERHAM
fits in another directory.  If no manual changes to the ERHAM
input file have been made then it is only necessary to update the MOLNAM.CAT file
in the AABS work directory.

Search the ERHAM output file for the word "derived" to jump to the end of 
the last iteration.

Search for "SUM OF STATES" to find candidate values for use as partition
function in generating the .CAT file.

When reusing an input file from ERHAM versions prior to R3 make sure to add 
suitable values of the scaling parameter SCPP (block 5 of input) at the end of 
each line defining the torsional parameters.  It is also necessary to add
a dummy SCPP value at the end of the line terminating the torsional
parameter input.


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Step 3:
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Transition entries will be added to MOLNAM.LIN with the quantisation 
defined by MOLNAM.CAT (IS1 as fourth quantum number and IS2 as eighth quantum 
number).

It is advisable to manually reorder transitions in the MOLNAM.LIN file as necessary, 
and to use end of line annotations of the same form as recognised by PIFORM
  


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Step 4:
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The settings necessary for operation of LINERH are to be placed in LINERH.INP,
typically:

             name of the input .LIN file:  molnam.lin
            name of the ERHAM input file:  molnam.in
       transitions (1) or full input (2):  2
    order of rotational qns in .LIN file:  1,2,3,5,6,7
                 symmetry labels IS1,IS2:  -4,-8
   ________________________________________
            d e s c r i p t o r            |_____ d a t a (starting on column 41)  
                                           

The previous version of the ERHAM input file MOLNAM.IN will be backed 
up to MOLNAM.IN.BAK.



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Step 5:
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It is necessary to set IFPR=4 in the ERHAM input file MOLNAM.IN (this
is the fifth parameter in the second line).  The preferred mode of operation is 
by means of the pipeline command:

ERHAMZ_R3<MOLRUN

where the file MOLRUN contains the responses to questions asked by the program:
input and output filenames, and the specification of the .CAT file, for example:

   molnam.in
   molnam.out
   molnam.cat
   1
   100000.
   -9.
   -9

NOTE: there is no automatic mechanism for updating the starting values of the
parameters in the ERHAM input, so that manual reediting is necessary.



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About step 6:
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ERHRES converts the MOLNAM.OUT file to:
   a) a formatted results file, typically named MOLNAM.RES
   b) a .LIN standard file containing transitions, typically named MOLNAM.LIN
      If a MOLNAM.LIN already exists it is backed up to MOLNAM.LIN.BAK

You need to fill out ERHRES.INP as required, typically:

            name of the ERHAM input file:  molnam.in
           name of the ERHAM output file:  molnam.out
             name of the RES output file:  molnam.res
             name of the LIN output file:  molnam.lin
   ________________________________________
            d e s c r i p t o r            |_____ d a t a (starting on column 41)  

The operation sequence LINERH->ERHAMZ_R3->ERHRES should be neutral regarding
the MOLNAM.LIN file.  If there was no additional editing then the .LIN file 
resulting from ERHRES should be identical to the one used as data for LINERH.

The previous version of the MOLNAM.LIN file will be backed up to MOLNAM.LIN.BAK.

This procedure also allows taking account of any editing made inside 
the MOLNAM.IN file, as MOLNAM.LIN resulting from this step should reflect these.


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