docs: def calculate_omega_matrix(states, Omega=1):
      """Calculate the matrix of transition frequencies.
  
      This function recieves a list of states and returns the corresponding
      omega_ij matrix, rescaled to units of Omega. These are understood to be
      absolute frequencies (as opposed angular frequencies).
      """
      N = len(states)
      omega = [[2*Pi*(states[i].nu-states[j].nu)/Omega
                for j in range(N)] for i in range(N)]
  
      return omega