Fourier Transform Spectroscopy with Long Absorption Path Length in Solid Hydrogen: Measurement ofΔJ=6andΔJ=8Transitions

New features in the infrared spectrum of solid parahydrogen were measured with high resolution (FWHM = 0.006 ${\mathrm{cm}}^{-1\mathrm{}}$) and high sensitivity. Two features were assigned as the transitions $W_{0\leftarrow 0}\mathrm{}\left(1\right)\mathrm{}$ and $W_{1\leftarrow 0}\mathrm{}\left(1\right)\mathrm{}$ with a change in the angular momentum quantum number of $\Delta J=6\mathrm{}$, and one feature was assigned as the transition $Y_{0\leftarrow 0}\mathrm{}\left(0\right)\mathrm{}$ with $\Delta J=8\mathrm{}$. An optical multipass system consisting of two spherical mirrors delimits the sample and gives ideally seven passes through the solid. Wave numbers, linewidths, and intensity parameters are reported and the optical performance is described.