function index_ice_100K,wave_in

;-----------------------------------------------------------------
;
; purpose:
;  Get the refractive index for ice at 100K (Bertie et al., 
;  J. Phys. Chem.,  50, p4501, 1969),  at the specified wavelength.
;
; input:
;    wave_in..........wavelength,  microns
;
; output:
;    index_ice_100K...complex refractive index
;
; source: Mark Hervig 
;
;-----------------------------------------------------------------

     numw = 59             ; # wavelengths
     wave = fltarr(numw)   ; 1/cm
     dxi  = fltarr(numw)   ; real index
     dxr  = fltarr(numw)   ; imaginary index

     waves='500.0  600.0  700.0  750.0  800.0  850.0  900.0  950.0 1000.0 '+$
           '1050.0 1100.0 1200.0 1300.0 1400.0 1500.0 1600.0 1650.0 1700.0 '+$
           '1800.0 2000.0 2200.0 2250.0 2300.0 2400.0 2600.0 2700.0 2800.0 '+$
           '2900.0 3000.0 3050.0 3100.0 3150.0 3200.0 3220.0 3250.0 3300.0 '+$
           '3350.0 3400.0 3450.0 3500.0 3600.0 3700.0 3800.0 4000.0 4400.0 '+$
           '4800.0 4950.0 5000.0 5200.0 5500.0 6000.0 6100.0 6200.0 6300.0 '+$
           '6675.0 6900.0 7200.0 7500.0 8000.0'
     reads,waves,wave

     wave = 10000./wave ; cm-1 to um

     dxrs='1.426  1.470  1.514  1.566  1.523  1.346  1.217  1.114  1.190  1.261  '+$
          '1.292  1.312  1.328  1.336  1.336  1.325  1.317  1.311  1.316  1.341  '+$
          '1.358  1.356  1.354  1.353  1.364  1.395  1.414  1.423  1.532  1.588  '+$
          '1.734  1.669  1.577  1.375  1.098  1.070  1.061  1.025  1.019  1.075  '+$
          '1.134  1.178  1.206  1.236  1.264  1.277  1.280  1.281  1.283  1.288  '+$
          '1.293  1.293  1.294  1.295  1.297  1.297  1.299  1.300  1.301'
     reads,dxrs,dxr

     dxis='1.78e-02 6.25e-02 1.08e-01 1.63e-01 3.28e-01 3.79e-01 3.20e-01 1.72e-01 '+$
          '3.18e-02 2.07e-02 3.79e-02 3.68e-02 3.95e-02 4.71e-02 5.61e-02 5.95e-02 '+$
          '5.64e-02 4.42e-02 2.38e-02 1.35e-02 2.78e-02 2.91e-02 2.54e-02 1.84e-02 '+$
          '8.66e-03 6.20e-03 6.96e-03 1.44e-02 4.44e-02 7.78e-02 2.79e-01 5.66e-01 '+$
          '7.00e-01 8.15e-01 5.83e-01 3.81e-01 2.98e-01 2.15e-01 1.07e-01 5.36e-02 '+$
          '1.74e-02 1.48e-03 6.50e-04 6.90e-04 5.00e-04 1.48e-03 2.01e-03 1.94e-03 '+$
          '8.50e-04 3.80e-04 5.50e-04 6.20e-04 5.00e-04 6.10e-04 6.60e-04 2.40e-04 '+$
          '9.50e-05 4.60e-05 0.00e+00'
     reads,dxis,dxi

;---- interpolate index to wave_in

      if (wave_in le wave(0) and wave_in ge wave(numw-1) ) then begin

        for i = 0,(numw-2) do begin

          if (wave(i) ge wave_in and wave(i+1) lt wave_in) then begin

            term   = (wave_in-wave(i)) /(wave(i+1)-wave(i))
            dr     = term * (dxr(i+1)-dxr(i)) + dxr(i)
            di     = term * (dxi(i+1)-dxi(i)) + dxi(i)
            result = complex(dr,di)
            goto,jump1

          endif
        endfor

      endif

      print  ,wave_in,' not in range in index_ice_100K.pro'
      result = complex(0.0,0.0)
      jump1:

      return,result
      end