Different species for secondary electrons

The option to have a different species than the impacting electron for
secondary electrons from ionization is introduced.

src/modules/init/moduleInput.f90

@@ -634,7 +634,7 @@ MODULE moduleInput
       INTEGER:: i, k, ij
       INTEGER:: pt_i, pt_j
       REAL(8):: energyThreshold, energyBinding
-      CHARACTER(:), ALLOCATABLE:: electron
+      CHARACTER(:), ALLOCATABLE:: electron, electronSecondary
       INTEGER:: e
       CLASS(meshCell), POINTER:: cell
 
@@ -711,8 +711,16 @@ MODULE moduleInput
                 IF (.NOT. found) CALL criticalError('energyThreshold not found for collision' // object, 'readInteractions')
                 CALL config%get(object // '.electron', electron, found)
                 IF (.NOT. found) CALL criticalError('electron not found for collision' // object, 'readInteractions')
-                CALL initBinaryIonization(interactionMatrix(ij)%collisions(k)%obj, &
-                                          crossSecFilePath, energyThreshold, electron)
+                CALL config%get(object // '.electronSecondary', electronSecondary, found)
+                IF (found) THEN
+                  CALL initBinaryIonization(interactionMatrix(ij)%collisions(k)%obj, &
+                                            crossSecFilePath, energyThreshold, electron, electronSecondary)
+
+                ELSE
+                  CALL initBinaryIonization(interactionMatrix(ij)%collisions(k)%obj, &
+                                            crossSecFilePath, energyThreshold, electron)
+
+                END IF
 
               CASE ('recombination')
                 !Electorn impact ionization