Vibrational and Geometric Structures of La 3 C 2 O and La 3 C 2 O + from MATI Spectra and ab initio Calculations Mourad ROUDJANE, Lu WU, and Dong-Sheng YANG Department of chemistry, University of Kentucky

Outline o Introduction o Experimental setup o Theoretical calculations o Results o Conclusions

Introduction  Gas phase molecular clusters have been subject to numerous spectroscopic investigations as ideal systems to understand intermolecular structures and interactions at the microscopic level. Metal oxide clusters: M n O m Metal carbide clusters: M n C m Metal nitride clusters: M n N m M = ( group III transition metals, and Lanthanides )

La 3 C 2 La 3 C 2 O La 3 C 3 TOF of La with C 2 H 4 at 240 nm UV laser Oxygen is more reacting with La than carbon C !!!

 Accurate measurements of the ionization energy and vibrational frequencies of La 3 C 2 O  Geometries and electronic ground states for the neutral and ion using ab initio calculations Objectives La 3 C 2 O, La 3 C 2 O + La 3 C 2, La 3 C 2 + How does oxygen coordination affect La 3 C 2 structure ?

EXPERIMENTAL SETUP Source chamber Detection Spectrometer Turbo pumpDiffusion pump HV Gate Valve

EXPERIMENTAL SETUP Cluster beam Source and Pulsed Valve Carrier Gas Mixture Extraction Can MCP  -Metal Shielding Turbo pumpDiffusion pump HV Gate Valve TOF SHG 532 nm La 3 C 2 O

PFI-PIE of La 3 C 2 O PIE~30850 cm -1 Ligand : ethylene C 2 H 4 O 2 from carrier gas 50 psi He

+ ~ 1-10VDC UV laser 320 V/cm Ion Neutral Rydberg states MATI-detection EXPERIMENTAL SETUP

MATI SPECTRA OF La 3 C 2 O E f =3.6 V/cm DC E f =1.6 V/cm DC 0-0 AIE= (5) cm -1 ΔE=6.1*(E f ) ? AIE = cm -1

COMPUTATIONS  Density functional theory for geometrical optimization and frequencies calculations (GAUSSIAN 03) B3LYP, MP G(d,p) {C, O} LanL2DZ, Stuttgart RSC Segmented/ECP {La} Multidimensional Franck-Condon factor calculations  Spectral simulation at finite temperature using a Boltzmann distribution

C 2v Geometries : Minimum Energy Structures ΔE = 4780 cm -1 MP2 level calculations CsCs

Theoretical Results E(cm -1 ) 2 A 1 (0) 4 A 2 (15322) 1 A 1 (29865) 3 A 2 (37367 ) Exp.IE(30850) ion neutral States, relative energies, electronic transitions and AIE using MP2 level calculations with Stuttgart RSC Segmented/ECP/6-311+g(d,p). ΔS=±1

1 A 1 2 A 1 3 A 2 2 A 1 3 A 2 4 A K Stuttgart RSC Segmented /ECP Simulations vs Experiment Spectra LanL2DZ

1 A 1 2 A 1 AIE = cm n05n n03n Simulations vs Experiment Spectra

Exp frequencies (cm -1 )Theo frequencies (cm -1 ) ν + 2 (a 1 )= 629 (theo) ν + 3 (a 1 )= 540 ν + 1 (a 1 )= 680 ν + 5 (a 1 ) =168 ν + 4 (a 1 )= 238 ν 9 (b 1 ) =46 ν 9 (b 1 ) =19

La (2) -La (1) La (1) -La (3) C-La (2) C-La (3) C-C La 3 C 2 2 B 2 (C 2v ) La 3 C A’ 1 (D 3h ) Atomic distances (Å) using B3LYP calculations with Lanl2DZ/6-311+G(d,p) La (2) -La (1) La (1) -La (3) C-La (2) C-La (3) C-CLa 2 -OLa 3 -O La 3 C 2 O 2 A 1 (C 2v ) La 3 C 2 O + 1 A 1 (C 2v ) Oxygen Coordination with La 3 C 2

Side Top HOMO of 2 A 1 6s mixed with 5d orbital of La(2) HOMO of 2 B 2 6s mixed with 5d orbital of La(1) and La(3) Side Molecular Orbitals

MoleculeAIE(cm -1 ) Exp/Theo Frequency (cm -1 ) 1 A 1 2 A 1 La 3 C 2 O30891(5)/29865ν + =(160, 230, 530, 665/164,238,540,671) ν =155/160 CONCLUSIONS AIE and vibrational modes of La 3 C 2 O and La 3 C 2 O + using MATI spectroscopy Structures of the ground states of La 3 C 2 O and La 3 C 2 O + using ab initio calculations AIE(La 3 C 2 O) > AIE(La 3 C 2 ) Effect of oxygen coordination on the structure La 3 C 2

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