c=======================================================================

      subroutine cxdta (cprime,v,iwl,iwh,cp,ind) 11
c     this subroutine finds the cprime for the wavenumber v.
c     input:         v --- wavenumber
c            (iwl,iwh) --- wavenumber pair specifies the absorption
c                          region. both are arrays and terminated
c                          with the value -999
c                   cp --- array contains the cprimes
c     output:   cprime --- the cprime corresponding to v
c     i/o:         ind --- indicator indicates the absorption region
c                          where the wavenumber is expected to be in
c                          or nearby (it serves for the purpose
c                          to speed up the searching process)
      dimension iwl(*),iwh(*),cp(*)
      iv=v
      cprime=-20.0
      if (iwl(ind+1) .eq. -999 .and. iv .gt. iwh(ind)) return
      if (iv .lt. iwl(1)) return
      ic=0
  100 if (iv .ge. iwl(ind) .and. iv .le. iwh(ind)) go to 200
      if (iv .gt. iwh(ind) .and. iv .lt. iwl(ind+1)) return
      ind=ind+1
      if (iwl(ind) .ne. -999) go to 100
      ind=ind-1
      if (iv .gt. iwh(ind)) return
      ind=1
      go to 100
  200 if (ind .eq. 1) go to 400
      indm1=ind-1
      do 300 i=1,indm1
        ic=ic+(iwh(i)-iwl(i))/5+1
  300 continue
  400 ic=ic+(iv-iwl(ind))/5+1
      cprime=cp(ic)
      return
      end