Infrared Observation of the ν 1 (  ) and ν 2 (  ) Stretching Modes of Linear GeC 3 E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham Department of Physics and Astronomy Texas Christian University Fort Worth, TX rd Meeting of the International Symposium on Molecular Spectroscopy The Ohio State University June 16-20, 2008

2 Motivation Form novel germanium-carbon clusters by single laser ablation of germanium-carbon sintered rods. Target GeC 3 molecule that had not been observed when GeC 3 Ge and GeC 3 Si were discovered (Robbins et al, JCP. 2001,2002) Identify structure via isotopic shift measurements and assign the vibrational fundamentals

3 Quartz window Ge/C/Si sintered rod Ar flow FTIR (MCT detector) ~10 -8 Torr CsI window Gold mirror held held at ~10 K Experimental Setup laser focusing lens Nd-YAG 1064 nm pulsed laser, 0.2 to 3.0 Watts See MJ06 for an animated schematic of the dual ablation set up

4 Germanium carbon clusters Linear GeC 3 Ge was previously produced by dual laser ablation of germanium and carbon rods. The ν 3 (  u ) fundamental was assigned at cm -1 (D.L. Robbins et al, J. Chem. Phys ) Small germanium-carbon clusters have been investigated by Leszczynski et al. using DFT, MP2, CCSD, and CCSD(T) levels of theory (Leszczynski et. al. J. Chem. Phys. 2005) Previous Work

5 In later work using single laser ablation of a sintered germanium-carbon rod the yield of GeC 3 Ge was improved allowing the observation of the next most intense infrared active modes The ν 4 (  u ) stretching mode was assigned to cm -1 ( ) and the bending mode ν 6 (π u ) was assigned to 580.1cm -1 (to be published) Previous Work

, , Ge/ 12 C rod Simulation Frequency (cm -1 ) The ν 4 (  u ) stretching mode of linear GeC 3 Ge (to be published)

7 Germanium, carbon, and silicon mixed cluster Linear GeC 3 Si was previously produced by dual laser ablation of Ge/C and Si/C rods. The ν 1 (  ) fundamental was assigned at cm -1 (D.L. Robbins et al, J. Chem. Phys ) In later work using single laser ablation of a sintered Ge/Si/C rod the yield of GeC 3 Si was improved. The ν 4 (  ) stretching mode and the bending mode ν 6 (π) are tentatively assigned at cm -1 and cm C isotopic data are required to confirm the assignments Previous Work

, cm , cm , cm , cm -1 Frequency (cm -1 ) The “ ν 4 (  )” stretching mode of linear GeC 3 Si

Frequency (cm -1 ) (a) 20% 13 C/Ge/Si sintered rod GeC 3 Si (B3LYP/cc-pVDZ) Linear GeC 3 or SiC 3 ?

Frequency (cm -1 ) (a) 35% 13 C/Ge sintered rod Linear GeC 3

11 GeC 3 isomers (Leszczynski et al. J. Chem. Phys. 2005) +2.1 kcal/mol +9.2 kcal/mol 0 kcal/mol kJ/mol kite fan linear MP2 (CCSD) [DFT]

(b 2 ) (b 2 ) (b 1 ) (a 1 ) (a 1 ) (a 1 ) DFT Calculated (cm -1 ) Vibrational mode Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory kcal/mol kite

(b 2 ) (b 2 ) (b 1 ) (a 1 ) (a 1 ) (a 1 ) DFT Calculated (cm -1 ) Vibrational mode Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory +7.4 kcal/mol fan

( π ) ( π ) ( σ ) ( σ ) ( σ ) DFT Calculated (cm -1 ) Vibrational mode Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory 0 kcal/mol linear

(a) DFT Simulation (b) 35% 13 C/Ge sintered rod , , 74 – , , , , B CD, E F G H A Frequency (cm -1 )

16 The ν 2 ( σ ) mode of linear GeC 3 a DFT calculations scaled by two scaling parameters function (R. H. Kranze et al.,JCP 1995) :

( π ) ( π ) ( σ ) ( σ ) ( σ ) DFT Calculated (cm -1 ) Vibrational mode Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory ~ 5.3 times the intensity of the cm -1 band

Frequency (cm -1 ) C3C3 C9C9 C 6 C7C7     GeC 3 Ge ~9 peaks/10 cm -1 (a) 35% 13 C/Ge sintered rod

(b) Ablation of C rod Cn?Cn? C6-C6- ● C 6 C7C7 GeC 3 Ge n C m ? GeC 9 GeC 3 Ge ν5ν5 ν3ν3 ν 1 ? ν5ν5 ●● ● GeCO GeCO site ♦ ♦ ♦ ♦ ♦ ♦ unidentified weak features ● C 6 natural enrichment single substitutions (a)Simultaneous ablation of 5% 13 C and Ge rods

(a) DFT Simulation (b) 5% 13 C and Ge dual ablation ♦ ♦ ♦ ♦ GeCO GeCO site GeC 3 Ge ν3ν Ge 13 CO Ge 13 CO site ν 3 GeC 3 Ge all 13 C isotopic shifts C7C7 ν5ν5 ▪ ν 5 C 7 single 13 C isotopic shifts ▪ ▪ ▪ ▲ ν 4 C 6 13 C isotopic shift ▲ GeC 3 ν1ν A BC D , , ,

21 The ν 1 ( σ ) mode of linear GeC 3 a DFT calculations scaled by one scaling parameter :

22 Laser ablation technique vs. GeC 3 isomers initial geometry convergence We have experimental evidence that the laser ablation technique produces similar to Knudsen evaporation cell evaporation (Drowart et al., JCP 1959) 10% C 2 30% C 1 60% C 3

23 Laser ablation technique vs. GeC 3 isomers We have experimental evidence that the laser ablation technique produces similar to Knudsen evaporation cell evaporation (Drowart et al., JCP 1959) 10% C 2 30% C 1 60% C 3 initial geometry convergence

24 Laser ablation technique vs. GeC 3 isomers initial geometry convergence We have experimental evidence that the laser ablation technique produces similar to Knudsen evaporation cell evaporation ( Drowart et al., JCP 1959 ) 10% C 2 30% C 1 60% C 3

25 Conclusions DFT calculations with B3LYP/cc-pVDZ level of theory predict the kite, fan, and linear isomers within a few kcal/mol. We think that the laser ablation technique favors the fan and linear isomers over the kite No experimental evidence of kite structure for MC 3 (M= Ge, Cr, Co, Al, Ti, Sc, Cu) (Kinzer et al., JCP. 2006,2008; Bates et al., JCP, 2006,2007,2008; Vala et al. JCP 2008) Linear GeC 3 was formed by the laser ablation technique. The ν 1 ( σ ) and ν 2 ( σ ) stretching modes have been observed at and cm -1 respectively

26 Acknowledgments Our group would like to acknowledge funding from Welch Foundation TCU Research and Creative Activities Fund (TCURCAF) W.M. Keck Foundation Great appreciation for David Yale (machine shop) Mike Murdock (machine shop) Jerry Katchinska (electronics shop)