From bce32ef6fb7df36676a9670306a1f3cd852bb2f9 Mon Sep 17 00:00:00 2001
From: Weijian Lin <84821747+wlin6927@users.noreply.github.com>
Date: Mon, 20 Nov 2023 18:10:04 -0500
Subject: [PATCH] Update species.py to include H- as a species

---
 pmd_beamphysics/species.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/pmd_beamphysics/species.py b/pmd_beamphysics/species.py
index 65bd004..9cd9f4b 100644
--- a/pmd_beamphysics/species.py
+++ b/pmd_beamphysics/species.py
@@ -9,22 +9,27 @@
 mec2 = scipy.constants.value('electron mass energy equivalent in MeV')*1e6
 mpc2 = scipy.constants.value('proton mass energy equivalent in MeV')*1e6
 
+mhmc2 = mpc2 + mec2 * 2 # H- mass energy equivalent in MeV
+
 e_charge = scipy.constants.e
 c_light = scipy.constants.c
 
 CHARGE_OF = {'electron': -e_charge,
             'positron': e_charge,
-            'proton': e_charge}
+            'proton': e_charge,
+            'H-': -e_charge}
 
 CHARGE_STATE = {
     'electron': -1,
     'positron': 1,
-    'proton': 1}
+    'proton': 1,
+    'H-': -1}
 
 
 MASS_OF = {'electron': mec2,
            'positron': mec2,
-           'proton': mpc2}
+           'proton': mpc2,
+           'H-': mhmc2}
 
 
 
@@ -51,4 +56,4 @@ def charge_state(species):
     raise ValueError(f'Species not available: {species}')    
     
     
-    
\ No newline at end of file
+