diff --git a/four_levels_model.py b/four_levels_model.py
index f05c54e..8fdbad7 100644
--- a/four_levels_model.py
+++ b/four_levels_model.py
@@ -375,7 +375,8 @@ class HeatingGas:
                                         self.energy[energy_range_power_absorbed]) #erg s-1
         heating_pah_dc = np.trapz(photo_absorption_dc[energy_range_power_absorbed],\
                                         self.energy[energy_range_power_absorbed]) #erg s-1
-               
+        #power absorbed by each PAH charge state   
+        
         ''' total power of the radiation absorbed by pahs '''
         total_absorbed_radiation_power = self.frac_anion   * heating_pah_a +\
                                          self.frac_neutral * heating_pah_n +\
@@ -390,4 +391,4 @@ class HeatingGas:
         self.total_gas_heating = total_injected_power * (self.fc_pah/self.n_c) * 2.7e-4
         #2.7e-4 : elemental abundance of C relative to H (Tielens 2021)  
                 
-        return self.total_gas_heating, self.g_0 , self.gamma,  self.t_gas, self.n_e, self.n_c
\ No newline at end of file
+        return self.total_gas_heating, self.g_0 , self.gamma, self.t_gas, self.n_e, self.n_c
\ No newline at end of file
--
libgit2 0.21.2