The M-Series Absorption Spectra of Metallic Platinum and Gold

The $M$-absorption spectra of metallic platinum (78) and gold (79) have been investigated by the use of a vacuum spectrograph. Five discontinuities were found for platinum at 5.711A ($M_1$), 5.506A ($M_2$), 4.677A ($M_3$), 4.085A ($M_4$), and 3.742A ($M_5$). For gold four were found at 5.506A ($M_1$), 5.315A ($M_2$), 4.501A ($M_3$) and 3.603A ($M_5$). No $M_4$ discontinuity was found for gold and the $M_4$ for platinum was very faint. The ${\left(\frac{\nu }{R}\right)}^{\frac{1}{2}}$ values for the experimentally determined edges compare very favorably with the values predicted by the use of absorption and emission data from the $L$-series except in the case of $M_1$ and $M_2$ where an unmistakable deviation, previously reported by other investigators on other elements, appears to be confirmed. No measurable shift in the position of any of the discontinuities due to a change in valence of four, in the case of the platinum atom, was observed. No "white line" absorption was observed at any of the discontinuities.