fix bug disperse; add readme.pdf

SpecDisperser/SpecDisperser.py

 '''
 Author: zx
 Date: 2021-04-08 13:49:35
-LastEditTime: 2022-05-20 08:45:03
+LastEditTime: 2022-06-28 19:20:23
 LastEditors: xin zhangxinbjfu@gmail.com
 Description: In User Settings Edit
 FilePath: /undefined/Users/zhangxin/Work/SlitlessSim/sls_lit_demo/SpecDisperser/SpecDisperser.py

SpecDisperser/disperse_c/interp.pyx

@@ -189,7 +189,7 @@ def interp_conserve_c(np.ndarray[DTYPE_t, ndim=1] x, np.ndarray[DTYPE_t, ndim=1]
             if (templmid[k+1] == tlam[i]) & (i < ntlam):
                 h = tlam[i]-tlam[i-1];
                 numsum+=h*(tf[i]+tf[i-1]);
-            else:
+            elif (i < ntlam):
                 i-=1;
                 h = templmid[k+1]-tlam[i];
                 numsum+=h*(tempfmid[k+1]+tf[i]);