Update input.cc

input.cc

@@ -591,21 +591,22 @@ void add_transitions_to_unsorted_linelist(const int element, const int ion, cons
         const float f_ul = g_ratio * ME * pow(CLIGHT, 3) / (8 * pow(QE * nu_trans * PI, 2)) * transition.A;
 
         const int nupperdowntrans = get_ndowntrans(element, ion, level);
-        auto &downtransition =
-            temp_alltranslist[globals::elements[element].ions[ion].levels[level].alltrans_startdown + nupperdowntrans];
+        auto &downtransition = temp_alltranslist[globals::elements[element].ions[ion].levels[level].alltrans_startdown +
+                                                 nupperdowntrans - 1];
 
         // this is what classic did, but it is not quite correct. The downtrans list should be searched to find the
         // correct index, not just using the last one. It probably works for the case where the transitions are sorted,
         // but the assertion tripped on C IV in the classic dataset.
-        // assert_always(downtransition.targetlevelindex == lowerlevel);
+        assert_always(downtransition.targetlevelindex == lowerlevel);
 
         downtransition.einstein_A += transition.A;
         downtransition.osc_strength += f_ul;
         downtransition.coll_str = std::max(downtransition.coll_str, transition.coll_str);
 
         const int nloweruptrans = get_nuptrans(element, ion, lowerlevel);
         auto &uptransition =
-            temp_alltranslist[globals::elements[element].ions[ion].levels[lowerlevel].alltrans_startup + nloweruptrans];
+            temp_alltranslist[globals::elements[element].ions[ion].levels[lowerlevel].alltrans_startup + nloweruptrans -
+                              1];
 
         // as above, the downtrans list should be searched to find the correct index instead of using the last one.
         // assert_always(uptransition.targetlevelindex == level);