qspec.mass_factor  (  m0 ,  m1 ,  m0_d ,  m1_d  )[source]

The specific mass factor required to calculate modified isotope shifts or charge radii and its uncertainty $$\begin{aligned} \mu &= \frac{m_0 m_1}{m_0 - m_1}\\ \Delta\mu &= \mu\sqrt{\left(\frac{\Delta m_0}{m_0} - \frac{\Delta m_0}{m_0 - m_1}\right)^2 + \left(\frac{\Delta m_1}{m_1} + \frac{\Delta m_1}{m_0 - m_1}\right)^2}. \end{aligned}$$ Use $m_0 = M_0 + m_\mathrm{e}$ and/or $m_1 = M_1 + m_\mathrm{e}$ with the nuclear masses $M_0$ and $M_1$ and the electron mass $m_\mathrm{e}$ for King-plots. Compare (6.4) with (3.17) in [W. H. King, Isotope shifts in atomic spectra (1984)].

Parameters:

m0array_like

The mass $m_0$ of the first isotope (u).

m1array_like

The mass $m_1$ of the second isotope (u).

m0_darray_like

The mass uncertainty $\Delta m_0$ of the first isotope (u).

m1_darray_like

The mass uncertainty $\Delta m_1$ of the second isotope (u).

Returns:

(mu, mu_d)(ndarray, ndarray)

The mass factor $\mu$ and its uncertainty $\Delta\mu$ required to calculate modified isotope shifts or charge radii.