Absorption and Laser-Excited Fluorescence of Matrix-Isolated CuO

Absorption and laser‐excited fluorescence spectra of CuO trapped in variousmatrices have been observed. The matrix data and previously observed gas‐phase data are consistent with $$\begin{array}{ccccc}& {\nu }_{00}\mathrm{(martix)}& {\nu }_{00}{\mathrm{(gas)}}^5& \mathrm{\nu \; (martix)}& \\ & {\mathrm{(cm}}^{\text{−1}})& {\mathrm{(cm}}^{\text{−1}})& {\mathrm{(cm}}^{\text{−1}})& {\mathrm{(cm}}^{\text{−1}})\\ C& & \text{23 550}& & \\ {\mathrm{B(}}^2\mathrm{\Sigma ?)}& \text{20 490}& \text{20 953}& 624& \\ {\mathrm{A(}}^2\mathrm{\Pi ?)}& \text{3 900}& \text{4 460}& 605& {(}^2{\Pi }_{\text{1/2}}{\mathrm{\hspace{0.17em}-\hspace{0.17em}}}^2\text{Π3/2\hspace{0.17em}=\hspace{0.17em}275)}\\ {\mathrm{X(}}^2\mathrm{\Pi )}& 0& 0& 665& {(}^2{\Pi }_{\text{1/2}}{\mathrm{\hspace{0.17em}-\hspace{0.17em}}}^2{\Pi }_{\text{3/2}}\text{\hspace{0.17em}≃\hspace{0.17em}200)}\end{array}$$ for the lowest states of CuO. It is shown that the matrix‐isolation technique can beused to “tune” an absorption into coincidence with a laser line in order to observefluorescence. The vibrational relaxation of CuO in a solid matrix requires on the order of 10⁵ vibrations.