Some more cleanups, especially tests

examples/ion_rate_plot.py

@@ -0,0 +1,19 @@
+import matplotlib.pyplot as plt
+import numpy as np
+
+import scgenerator as sc
+
+
+def field(t: np.ndarray, fwhm=10e-15) -> np.ndarray:
+    t0 = sc.pulse.width_to_t0(fwhm, "gaussian")
+    return sc.pulse.initial_full_field(t, "gaussian", 1e-4, t0, 2e14, sc.units.nm(800), 1)
+
+
+rate = sc.plasma.create_ion_rate_func(sc.materials.Gas("argon").ionization_energy)
+
+fig, (top, mid, bot) = plt.subplots(3, 1)
+t = np.linspace(-10e-15, 10e-15, 1024)
+E = field(t)
+top.plot(t * 1e15, field(t))
+mid.plot(t * 1e15, rate(np.abs(E)))
+plt.show()