def t_pulse(t_2, f_2, f, DM):
    """
    Function for generating the time values of a pulse given the frequency
    values. Eq. 1 in FDMT paper.
    t_pulse, t_2 in s
    f_2, f in MHz
    DM in pc cm^-3
    """
    return t_2 + 4.148808*DM*((f/1000.)**(-2) - (f_2/1000.)**(-2))/1000.