15min:

SUDESH KUMARI, MOURAD ROUDJANE AND DONG-SHENG YANG, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055.

Hydrogen elimination is observed in the reaction of laser-ablated La atoms and ethylene (C₂H₄) in a pulsed molecular beam source. Dehydrogenated products, La(C₂H₂) and La(C₄H₆), 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(C₂H₂) is determined as a triangle (C_2v) in the ²A₂ ground electronic state, where La binds with C₂H₂ in a two-fold mode ( ²). La(C₄H₆) is identified as a diligand species with La being sandwiched between C₂H₂ and C₂H₄, each in a two-fold binding mode, and the complex is in the ²A₁ ground electronic state. The adiabatic ionization energies of La( ²-C₂H₂) and La( ²-C₂H₂)( ²-C₂H₄) are measured to be 41174(5) and 39405(5) cm^-1, respectively. La⁺-C₂H₂ and La⁺-C₄H₆ stretching and C-H bending frequencies of the corresponding ions are also determined, and the vibrational assignments are confirmed with deuterated ethylene measurements.