Optical Stark spectroscopy of the $\tilde B{}^1A^{\prime \prime} $B̃1A′′(000)←$\tilde X{}^1A^\prime $X̃1A′(000) system of copper hydroxide

The $\tilde B{}^1A^{\prime \prime} $B̃1A′′(000)←$\tilde X{}^1A^\prime $X̃1A′(000) band system of a cold beam of CuOH has been studied field-free and in the presence of a static electric field. The Stark tuning of the low-J levels of the $\tilde X{}^1A^\prime $X̃1A′(000) state were analyzed to give a value of 3.968(32) D for the a-component of the permanent electric dipole moment, μa. An upper limit of 0.3 D for μa($\tilde B{}^1A^{\prime \prime} $B̃1A′′) is established from the lack of observable Stark tuning for the low-J levels of the $\tilde B{}^1A^{\prime \prime} $B̃1A′′(000) state. The experimental value for μa($\tilde X{}^1A^\prime $X̃1A′) is compared to theoretical predictions and other Cu-containing molecules. A molecular orbital correlation diagram is used to rationalize the large change in μa upon excitation. The electronegativity of OH was determined to be 2.81 from a comparison of the determined μa with the experimental μ values for CuF, CuO, and CuS.