Knowledge Bank

Hydrogen elimination is observed in the reaction of laser-ablated La atoms and ethylene (C$2$H$4$) in a pulsed molecular beam source. Dehydrogenated products, La(C$2$H$2$) and La(C$4$H$6$), are identified by time-of-flight mass spectrometry and studied by pulsed-field-ionization zero-electron kinetic energy spectroscopy and density functional theory calculations. La(C$2$H$2$) is determined as a triangle (C) in the $2$A$2$ ground electronic state, where La binds with C$2$H$2$ in a two-fold mode ($\eta 2$). La(C$4$H$6$) is identified as a diligand species with La being sandwiched between C$2$H$2$ and C$2$H$4$, each in a two-fold binding mode, and the complex is in the $2$A$1$ ground electronic state. The adiabatic ionization energies of La($\eta 2$-C$2$H$2$) and La($\eta 2$-C$2$H$2$)($\eta 2$-C$2$H$4$) are measured to be 41174(5) and 39405(5) cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$, respectively. La$+$-C$2$H$2$ and La$+$-C$4$H$6$ stretching and C-H bending frequencies of the corresponding ions are also determined, and the vibrational assignments are confirmed with deuterated ethylene measurements.