Precision Determination of the Low-Lying Energy Levels of ${\mathrm{W}}^{182}$, ${\mathrm{W}}^{183}$, ${\mathrm{W}}^{184}$, and ${\mathrm{W}}^{186}$

The low-lying energy levels in the wolfram isotopes have been studied by using the 3.7-Mev proton beam of the A-48 high-current linear accelerator at the University of California Radiation Laboratory, Livermore, to excite the nuclei. The large beam currents available make it possible to use a bent-quartz-crystal spectrograph to observe the resultant $\gamma$ rays. With such an instrument, a resolution of better than 0.1% is possible. The following $\gamma$ rays have been observed: ${\mathrm{W}}^{182}$, 100.07±0.05 kev; ${\mathrm{W}}^{183}$, 46.508±0.030 kev and 52.612±0.030 kev; ${\mathrm{W}}^{184}$, 111.13±0.06 kev; ${\mathrm{W}}^{186}$, 122.48±0.08 kev. (Energies relative to W $K$-series x-rays.) The isotopic assignments are known from previous work on these lines. Known wavelengths of the $K$-series x-rays of wolfram and certain nuclear lines were used to calibrate the plate.