1. 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 76129 63 rd Meeting of the International Symposium on Molecular Spectroscopy The Ohio State University June 16-20, 2008

2. 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. 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. 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 1920.7 cm -1 (D.L. Robbins et al, J. Chem. Phys. 2001 ) 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. 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 735.3 cm -1 (74-12-12-12-74) and the bending mode ν 6 (π u ) was assigned to 580.1cm -1 (to be published) Previous Work

6. 6 720 725 730 735 740 745 750 738.3 70-12-12-12-70, 737.5 72-12-12-12-70, 736.7 74-12-12-12-70 72-12-12-12-72 735.3 74-12-12-12-74 76-12-12-12-72 734.5 76-12-12-12-74 736.0 74-12-12-12-72 Ge/ 12 C rod Simulation Frequency (cm -1 ) The ν 4 (  u ) stretching mode of linear GeC 3 Ge (to be published)

7. 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 1939.0 cm -1 (D.L. Robbins et al, J. Chem. Phys. 2002 ) 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 824.7 cm -1 and 590.5 cm -1. 13 C isotopic data are required to confirm the assignments Previous Work

8. 8 810 815 820 825 830 835 840 70-12-12-12-28, 826.0 cm -1 72-12-12-12-28, 825.3 cm -1 74-12-12-12-28, 824.7 cm -1 76-12-12-12-28, 824.2 cm -1 Frequency (cm -1 ) The “ ν 4 (  )” stretching mode of linear GeC 3 Si

9. 9 1220 1230 1240 1250 1260 1270 1280 1290 1279.6 1277.1 1254.5 1257.0 Frequency (cm -1 ) (a) 20% 13 C/Ge/Si sintered rod GeC 3 Si (B3LYP/cc-pVDZ) Linear GeC 3 or SiC 3 ?

10. 10 1220 1230 1240 1250 1260 1270 1280 1290 1279.6 Frequency (cm -1 ) (a) 35% 13 C/Ge sintered rod 1277.1 1257.0 1254.5 1277.1 1257.0 1232.71230.2 1252.7 1232.71230.2 1252.7 1232.71230.2 1254.5 1252.7 1232.71230.2 1257.0 1254.5 1252.7 1232.71230.2 1277.1 1257.0 1254.5 1252.7 1232.71230.2 Linear GeC 3

11. 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]

12. 12 323 6 (b 2 ) 1011 5 (b 2 ) 192 4 (b 1 ) 505 3 (a 1 ) 921 2 (a 1 ) 1409 1 (a 1 ) DFT Calculated (cm -1 ) Vibrational mode 31 3 11 40 28 155 Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory +11.1 kcal/mol kite

13. 13 313 6 (b 2 ) 1623 5 (b 2 ) 217 4 (b 1 ) 393 3 (a 1 ) 696 2 (a 1 ) 1136 1 (a 1 ) DFT Calculated (cm -1 ) Vibrational mode 4 84 40 19 29 4 Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory +7.4 kcal/mol fan

14. 14 143 5 ( π ) 408 4 ( π ) 466 3 ( σ ) 1300 2 ( σ ) 1986 1 ( σ ) DFT Calculated (cm -1 ) Vibrational mode 4 24 11 37 197 Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory 0 kcal/mol linear

15. 15 1220 1230 1240 1250 1260 1270 1280 1290 (a) DFT Simulation (b) 35% 13 C/Ge sintered rod 1277.1, 74-12-12-13 1232.7, 74 –13-12-13 1254.5, 74-13-12-12 74-12-13-13 1230.2, 74-13-13-13 1257.0, 74-12-12-13 1252.7, 74-13-13-12 B CD, E F G H A 1279.6 Frequency (cm -1 )

16. 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) :

17. 17 143 5 ( π ) 408 4 ( π ) 466 3 ( σ ) 1300 2 ( σ ) 1986 1 ( σ ) DFT Calculated (cm -1 ) Vibrational mode 4 24 11 37 197 Infrared Intensity (km/mole) Theoretical calculations using B3LYP/cc-pVDZ level of theory ~ 5.3 times the intensity of the 1279.6 cm -1 band

18. 18 2050 2000 1900 1950 Frequency (cm -1 ) C3C3 C9C9 C 6 C7C7     GeC 3 Ge ~9 peaks/10 cm -1 (a) 35% 13 C/Ge sintered rod

19. 19 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 (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 ●● ● 1952.5 1936.7 1903.9 1920.7 1928.3 1907.7 GeCO 1918.9 GeCO site ♦ ♦ ♦ ♦ ♦ ♦ unidentified weak features ● C 6 natural enrichment single substitutions (a)Simultaneous ablation of 5% 13 C and Ge rods

20. 20 1840 1850 1860 1870 1880 1890 1900 1910 1920 (a) DFT Simulation (b) 5% 13 C and Ge dual ablation ♦ ♦ ♦ ♦ 1907.7 GeCO 1918.9 GeCO site GeC 3 Ge ν3ν3 1920.7 1907.7 Ge 13 CO 1876.4 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 ν1ν1 1903.9 A BC D 1895.6, 74-12-12-13 1856.5, 74-12-13-12 1885.1, 74-13-12-12

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

22. 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. 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. 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. 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 1903.9 and 1279.6 cm -1 respectively

26. 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)