fix get_transition_for_states

atomic_physics/core.py

@@ -411,9 +411,13 @@ def get_transition_frequency_for_states(
         if relative:
             return f_rel
 
-        transition = self.get_transition_for_levels(
-            levels=(self.get_level_for_state(lower), self.get_level_for_state(upper))
-        )
+        lower_level = self.get_level_for_state(lower)
+        upper_level = self.get_level_for_state(upper)
+
+        if lower_level == upper_level:
+            return f_rel
+
+        transition = self.get_transition_for_levels(levels=(lower_level, upper_level))
         f_abs = f_rel + transition.frequency
 
         return f_abs

atomic_physics/tests/test_atom.py

@@ -199,6 +199,15 @@ def test_state_energies(self):
                 atol=1,
             )
 
+            np.testing.assert_allclose(
+                ion.get_transition_frequency_for_states(
+                    states=(F_4_ind, F_3_ind), relative=False
+                )
+                / (2 * np.pi),
+                ref_frequency * 1e9,
+                atol=1,
+            )
+
     def test_magnetic_dipoles(self):
         """
         Check the calculation for `state_vectors` for 43Ca+ at 146G against [1] table E.4.

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "atomic_physics"
-version = "2.0.0"
+version = "2.0.1"
 description = "Lightweight python library for calculations based on atomic structure"
 authors = ["hartytp <thomas.peter.harty@gmail.com>"]