Knowledge Bank

The H$2$-NH($X$) van der Waals complex has been examined using ab initio theory and detected via fluorescence excitation spectroscopy of the $A3\Pi$ - $X$$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma -$ transition. Electronic structure calculations show that the minimum energy geometry corresponds to collinear H$2$-NH($X$), with a well depth of D=116 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. The potential energy surface supports a secondary minimum for a T-shaped geometry, where the H atom of NH points towards the middle of the H$2$ bond (C$2v$ point group). For this geometry the well depth is 73 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$. Laser excitation spectra for the complex show transitions to the H$2$+NH($A$) dissociative continuum. The onset of the continuum establishes a binding energy of D$0$=32$\pm$2cm$^{-1}$ for H$2$-NH($X$). Fluorescence from bound levels of H$2$-NH($A$) was not detected, most probably due to rapid reactive decay (H$2$-NH($A$) $\to$ H+NH$2$). The complex appears to be a promising candidate for studies of the photo-initiated H$2$+NH abstraction reaction under conditions were the reactants are pre-aligned by the van der Waals forces.