diff --git a/src/celeritas/em/data/MollerBhabhaData.hh b/src/celeritas/em/data/MollerBhabhaData.hh
index ba45bba6c6..143cbf1c22 100644
--- a/src/celeritas/em/data/MollerBhabhaData.hh
+++ b/src/celeritas/em/data/MollerBhabhaData.hh
@@ -43,11 +43,6 @@ struct MollerBhabhaData
     //! Electron mass * c^2 [MeV]
     units::MevMass electron_mass;
 
-    //! Model's mininum energy limit [MeV]
-    static CELER_CONSTEXPR_FUNCTION units::MevEnergy min_valid_energy()
-    {
-        return units::MevEnergy{1e-3};
-    }
     //! Model's maximum energy limit [MeV]
     static CELER_CONSTEXPR_FUNCTION units::MevEnergy max_valid_energy()
     {
diff --git a/src/celeritas/em/interactor/detail/BhabhaEnergyDistribution.hh b/src/celeritas/em/distribution/BhabhaEnergyDistribution.hh
similarity index 100%
rename from src/celeritas/em/interactor/detail/BhabhaEnergyDistribution.hh
rename to src/celeritas/em/distribution/BhabhaEnergyDistribution.hh
diff --git a/src/celeritas/em/interactor/MollerBhabhaInteractor.hh b/src/celeritas/em/interactor/MollerBhabhaInteractor.hh
index a8a0444398..cf0037b550 100644
--- a/src/celeritas/em/interactor/MollerBhabhaInteractor.hh
+++ b/src/celeritas/em/interactor/MollerBhabhaInteractor.hh
@@ -18,6 +18,7 @@
 #include "celeritas/Constants.hh"
 #include "celeritas/Quantities.hh"
 #include "celeritas/em/data/MollerBhabhaData.hh"
+#include "celeritas/em/distribution/BhabhaEnergyDistribution.hh"
 #include "celeritas/em/distribution/MollerEnergyDistribution.hh"
 #include "celeritas/phys/CutoffView.hh"
 #include "celeritas/phys/Interaction.hh"
@@ -26,8 +27,6 @@
 #include "celeritas/random/distribution/BernoulliDistribution.hh"
 #include "celeritas/random/distribution/UniformRealDistribution.hh"
 
-#include "detail/BhabhaEnergyDistribution.hh"
-
 namespace celeritas
 {
 //---------------------------------------------------------------------------//
@@ -105,8 +104,6 @@ CELER_FUNCTION MollerBhabhaInteractor::MollerBhabhaInteractor(
 {
     CELER_EXPECT(particle.particle_id() == shared_.ids.electron
                  || particle.particle_id() == shared_.ids.positron);
-    CELER_EXPECT(electron_cutoff_
-                 >= value_as<Energy>(shared_.min_valid_energy()));
 }
 
 //---------------------------------------------------------------------------//
diff --git a/src/celeritas/em/model/MollerBhabhaModel.cc b/src/celeritas/em/model/MollerBhabhaModel.cc
index 44f59e8218..ba65b268d9 100644
--- a/src/celeritas/em/model/MollerBhabhaModel.cc
+++ b/src/celeritas/em/model/MollerBhabhaModel.cc
@@ -46,12 +46,12 @@ MollerBhabhaModel::MollerBhabhaModel(ActionId              id,
  */
 auto MollerBhabhaModel::applicability() const -> SetApplicability
 {
+    // TODO: potentially set lower energy bound based on (material-dependent)
+    // IonizationProcess lambda table energy grid to avoid invoking the
+    // interactor for tracks with energy below the interaction threshold
+
     Applicability electron_applic, positron_applic;
 
-    // The electron applicability.lower is twice the one for positrons due to
-    // its maximum transferable energy fraction being 0.5 (which is 1/2 the
-    // positron's). This prevents it to run an infinite number of Moller
-    // sampling loops.
     electron_applic.particle = interface_.ids.electron;
     electron_applic.lower    = zero_quantity();
     electron_applic.upper    = units::MevEnergy{interface_.max_valid_energy()};
diff --git a/src/celeritas/em/model/MuBremsstrahlungModel.cc b/src/celeritas/em/model/MuBremsstrahlungModel.cc
index 26d027e53f..e00c953f41 100644
--- a/src/celeritas/em/model/MuBremsstrahlungModel.cc
+++ b/src/celeritas/em/model/MuBremsstrahlungModel.cc
@@ -51,7 +51,7 @@ auto MuBremsstrahlungModel::applicability() const -> SetApplicability
     Applicability mu_minus_applic, mu_plus_applic;
 
     mu_minus_applic.particle = interface_.ids.mu_minus;
-    mu_minus_applic.lower    = interface_.min_incident_energy();
+    mu_minus_applic.lower    = zero_quantity();
     mu_minus_applic.upper    = interface_.max_incident_energy();
 
     mu_plus_applic.particle = interface_.ids.mu_plus;
diff --git a/src/celeritas/em/model/SeltzerBergerModel.cc b/src/celeritas/em/model/SeltzerBergerModel.cc
index 0d7d5cc92c..48893855df 100644
--- a/src/celeritas/em/model/SeltzerBergerModel.cc
+++ b/src/celeritas/em/model/SeltzerBergerModel.cc
@@ -84,8 +84,9 @@ SeltzerBergerModel::SeltzerBergerModel(ActionId              id,
  */
 auto SeltzerBergerModel::applicability() const -> SetApplicability
 {
-    // TODO: bounds need to be adjusted based on BremsstrahlungProcess data and
-    // SB table data
+    // TODO: potentially set lower energy bound based on (material-dependent)
+    // BremsstrahlungProcess lambda table energy grid to avoid invoking the
+    // interactor for tracks with energy below the interaction threshold
 
     Applicability electron_applic;
     electron_applic.particle = this->host_ref().ids.electron;
diff --git a/src/celeritas/phys/ParticleTrackView.hh b/src/celeritas/phys/ParticleTrackView.hh
index d8ae8d7205..892413f3ac 100644
--- a/src/celeritas/phys/ParticleTrackView.hh
+++ b/src/celeritas/phys/ParticleTrackView.hh
@@ -340,7 +340,7 @@ CELER_FUNCTION units::MevMomentumSq ParticleTrackView::momentum_sq() const
 {
     const real_type energy = this->energy().value();
     real_type result = energy * energy + 2 * this->mass().value() * energy;
-    CELER_ENSURE(result > 0);
+    CELER_ENSURE(result >= 0);
     return units::MevMomentumSq{result};
 }