diff --git a/.gitignore b/.gitignore
index 096c8e9..28ce419 100644
--- a/.gitignore
+++ b/.gitignore
@@ -98,6 +98,7 @@ ENV/
 
 # Spyder project settings
 .spyderproject
+.spyproject
 
 # Rope project settings
 .ropeproject
diff --git a/hack/add_de_Broglie_wavelength.py b/hack/add_de_Broglie_wavelength.py
new file mode 100644
index 0000000..f532c82
--- /dev/null
+++ b/hack/add_de_Broglie_wavelength.py
@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+"""
+Created on Thu Jul 14 11:19:59 2022
+
+@author: xuans
+"""
+
+import numpy as np
+
+import astropy.units as u
+
+from astropy.constants.si import k_B, h, m_e
+
+from plasmapy.utils.decorators import validate_quantities
+
+@validate_quantities(
+    T_e={'can_be_negative': False, 'equivalencies': u.temperature_energy()}    
+)
+def de_Broglie_wavelength(T_e: u.K) -> u.m:
+    constants = np.sqrt(h**2 / (2 * np.pi * m_e * k_B))
+    return constants * 1/np.sqrt(T_e)
+
+lambda_e = de_Broglie_wavelength