diff --git a/source/materials/MaterialProperties.cc b/source/materials/MaterialProperties.cc
index a5fefd80f..a0917e3ae 100644
--- a/source/materials/MaterialProperties.cc
+++ b/source/materials/MaterialProperties.cc
@@ -529,6 +529,8 @@ namespace materialprops {
     // May 2023:
     // Updated scintillation decay and yields from:
     // Triplet Lifetime in Gaseous Argon. Michael Akashi-Ronquest et al.
+    // Fano factor from M. Kase et al., NIMA, Volume 227, Issue 2 Pages 311-317
+    // Ionization energy from https://www.nuclear-power.com/argon-affinity-electronegativity-ionization/
 
     G4MaterialPropertiesTable* mpt = new G4MaterialPropertiesTable();
 
@@ -589,6 +591,8 @@ namespace materialprops {
     mpt->AddConstProperty("SCINTILLATIONYIELD2", .864);
     mpt->AddConstProperty("RESOLUTIONSCALE",    1.0);
     mpt->AddConstProperty("ATTACHMENT",         e_lifetime, 1);
+    mpt->AddConstProperty("IONIZATIONENERGY",    15.8 * eV, 1);
+    mpt->AddConstProperty("FANOFACTOR",            .2,      1);
 
     return mpt;
   }