diff --git a/Processes/Proposal/ContinuousProcess.cc b/Processes/Proposal/ContinuousProcess.cc
index 53eddcc85e810cd6cd1c00b99ee1033931209d65..9b5cdb848223970bfdedffce8ea4276291e7e085 100644
--- a/Processes/Proposal/ContinuousProcess.cc
+++ b/Processes/Proposal/ContinuousProcess.cc
@@ -18,18 +18,10 @@ namespace corsika::process::proposal {
   using namespace corsika::environment;
   using namespace corsika::units::si;
 
-  unordered_map<particles::Code, PROPOSAL::ParticleDef> ContinuousProcess::particles{
-      {particles::Code::Gamma, PROPOSAL::GammaDef()},
-      {particles::Code::Electron, PROPOSAL::EMinusDef()},
-      {particles::Code::Positron, PROPOSAL::EPlusDef()},
-      {particles::Code::MuMinus, PROPOSAL::MuMinusDef()},
-      {particles::Code::MuPlus, PROPOSAL::MuPlusDef()},
-      {particles::Code::TauPlus, PROPOSAL::TauPlusDef()},
-      {particles::Code::TauMinus, PROPOSAL::TauMinusDef()},
-  };
-
   bool ContinuousProcess::CanInteract(particles::Code pcode) const noexcept {
-    if (particles.find(pcode) != particles.end()) return true;
+    if (std::find(tracked_particles.begin(), tracked_particles.end(), pcode) !=
+        tracked_particles.end())
+      return true;
     return false;
   }
 
diff --git a/Processes/Proposal/ContinuousProcess.h b/Processes/Proposal/ContinuousProcess.h
index 7a42c122430eac408bf6939152d71edeba48dc9f..7e234ac632e3a01dd29164e14a6b5d34125f2e06 100644
--- a/Processes/Proposal/ContinuousProcess.h
+++ b/Processes/Proposal/ContinuousProcess.h
@@ -34,7 +34,11 @@ namespace corsika::process::proposal {
       : public corsika::process::ContinuousProcess<ContinuousProcess> {
     CORSIKA_ParticleCut& cut;
     corsika::random::RNG& fRNG;
-    static unordered_map<particles::Code, PROPOSAL::ParticleDef> particles;
+    static constexpr std::array<particles::Code, 7> tracked_particles{
+        particles::Code::Gamma,    particles::Code::Electron, particles::Code::Positron,
+        particles::Code::MuMinus,  particles::Code::MuPlus,   particles::Code::TauPlus,
+        particles::Code::TauMinus,
+    };
     unordered_map<const NuclearComposition*, PROPOSAL::Medium> media;
 
     bool CanInteract(particles::Code pcode) const noexcept;
diff --git a/Processes/Proposal/Interaction.cc b/Processes/Proposal/Interaction.cc
index 60ae3c81f64fdeeafed295838272e35357f58ccd..02b4b217ebbb199b3d06d8464a157d0e9e255c2c 100644
--- a/Processes/Proposal/Interaction.cc
+++ b/Processes/Proposal/Interaction.cc
@@ -19,18 +19,10 @@ namespace corsika::process::proposal {
   using namespace corsika::environment;
   using namespace corsika::units::si;
 
-  std::unordered_map<particles::Code, PROPOSAL::ParticleDef> Interaction::particles{
-      {particles::Code::Gamma, PROPOSAL::GammaDef()},
-      {particles::Code::Electron, PROPOSAL::EMinusDef()},
-      {particles::Code::Positron, PROPOSAL::EPlusDef()},
-      {particles::Code::MuMinus, PROPOSAL::MuMinusDef()},
-      {particles::Code::MuPlus, PROPOSAL::MuPlusDef()},
-      {particles::Code::TauPlus, PROPOSAL::TauPlusDef()},
-      {particles::Code::TauMinus, PROPOSAL::TauMinusDef()},
-  };
-
   bool Interaction::CanInteract(particles::Code pcode) const noexcept {
-    if (particles.find(pcode) != particles.end()) return true;
+    if (std::find(tracked_particles.begin(), tracked_particles.end(), pcode) !=
+        tracked_particles.end())
+      return true;
     return false;
   }
 
diff --git a/Processes/Proposal/Interaction.h b/Processes/Proposal/Interaction.h
index 6d0ad2f37c8b0183598cebed10fce5a37cd5d749..f3c3b2cf0b61b5a63524332f1f1a12f2b89a9827 100644
--- a/Processes/Proposal/Interaction.h
+++ b/Processes/Proposal/Interaction.h
@@ -17,7 +17,7 @@
 #include <corsika/process/particle_cut/ParticleCut.h>
 #include <corsika/random/RNGManager.h>
 #include <corsika/random/UniformRealDistribution.h>
-#include <unordered_map>
+#include <array>
 #include "PROPOSAL/PROPOSAL.h"
 
 using namespace corsika::environment;
@@ -32,7 +32,11 @@ namespace corsika::process::proposal {
   class Interaction : public corsika::process::InteractionProcess<Interaction> {
     CORSIKA_ParticleCut& cut;
     corsika::random::RNG& fRNG;
-    static std::unordered_map<particles::Code, PROPOSAL::ParticleDef> particles;
+    static constexpr std::array<particles::Code, 7> tracked_particles{
+        particles::Code::Gamma,    particles::Code::Electron, particles::Code::Positron,
+        particles::Code::MuMinus,  particles::Code::MuPlus,   particles::Code::TauPlus,
+        particles::Code::TauMinus,
+    };
     std::unordered_map<const NuclearComposition*, PROPOSAL::Medium> media;
 
     bool CanInteract(particles::Code pcode) const noexcept;