Initial commit

Base modular structure (phase space, Fermi function)
Initial .gitignore

beta_spectrum/utils.py

@@ -0,0 +1,9 @@
+# utils.py
+from .constants import HBAR_C_MEV_FM, ME_MEV
+
+
+def nuclear_radius(A: float) -> float:
+    r0_fm = 1.2  # fm
+    R_fm = r0_fm * A ** (1 / 3)
+
+    return R_fm / (HBAR_C_MEV_FM / ME_MEV)