Infrared Observation of the 1 and 2 Stretching

Infrared Observation of the ν 1( ) and ν 2( ) Stretching Modes of Linear Ge. C 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

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

Experimental Setup laser focusing lens Nd-YAG 1064 nm pulsed laser, 0. 2 to 3. 0 Watts Gold mirror held at ~10 K Quartz window FTIR (MCT detector) ~10 -8 Torr Cs. I window See MJ 06 for an animated schematic of the dual ablation set up Ge/C/Si sintered rod Ar flow 3

Previous Work n Germanium carbon clusters n Linear Ge. C 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 ) n Small germanium-carbon clusters have been investigated by Leszczynski et al. using DFT, MP 2, CCSD, and CCSD(T) levels of theory (Leszczynski et. al. J. Chem. Phys. 2005) 4

Previous Work n n In later work usingle laser ablation of a sintered germanium-carbon rod the yield of Ge. C 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(πu) was assigned to 580. 1 cm-1 (to be published) 5

The ν 4( u) stretching mode of linear Ge. C 3 Ge 736. 0 74 -12 -12 -12 -72 (to be published) 735. 3 74 -12 -12 -12 -74 76 -12 -12 -12 -72 734. 5 76 -12 -12 -12 -74 736. 7 74 -12 -12 -12 -70 72 -12 -12 -12 -72 737. 5 72 -12 -12 -12 -70, 738. 3 70 -12 -12 -12 -70, Ge/12 C rod Simulation 720 725 730 735 740 Frequency (cm-1) 745 750 6

Previous Work n Germanium, carbon, and silicon mixed cluster n Linear Ge. C 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 ) n In later work usingle laser ablation of a sintered Ge/Si/C rod the yield of Ge. C 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 7

The “ν 4( )” stretching mode of linear Ge. C 3 Si 74 -12 -12 -12 -28, 824. 7 cm-1 72 -12 -12 -12 -28, 825. 3 cm-1 70 -12 -12 -12 -28, 826. 0 cm-1 76 -12 -12 -12 -28, 824. 2 cm-1 810 815 820 825 830 835 840 Frequency (cm-1) 8

1279. 6 Ge. C 3 Si (B 3 LYP/cc-p. VDZ) 1254. 5 1257. 0 1277. 1 Linear Ge. C 3 or Si. C 3 ? (a) 20% 13 C/Ge/Si sintered rod 1220 1230 1240 1250 1260 1270 1280 1290 Frequency (cm-1) 9

1279. 6 Linear Ge. C 3 1220 1230 1277. 1 1252. 7 1230. 2 1254. 5 1257. 0 (a) 35% 13 C/Ge sintered rod 1240 1250 1260 1270 1280 1290 Frequency (cm-1) 10

Ge. C 3 isomers (Leszczynski et al. J. Chem. Phys. 2005) kite 0 kcal/mol MP 2 (CCSD) [DFT] fan +2. 1 kcal/mol k. J/mol linear +9. 2 kcal/mol k. J/mol 11

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

Theoretical calculations using B 3 LYP/cc-p. VDZ level of theory fan +7. 4 kcal/mol Vibrational mode DFT Calculated (cm-1) Infrared Intensity (km/mole) 1(a 1) 1136 4 2(a 1) 696 29 3(a 1) 393 19 4(b 1) 217 40 5(b 2) 1623 84 6(b 2) 313 4 13

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

1220 1230 H G F 1240 1250 1260 1277. 1, 74 -12 -12 -13 1257. 0, 74 -12 -12 -13 74 -12 -13 -13 1254. 5, 74 -13 -12 -12 1252. 7, 74 -13 -13 -12 1230. 2, 74 -13 -13 -13 1232. 7, 74 – 13 -12 -13 (b) 35% 13 C/Ge D, E C B 1270 1279. 6 sintered rod A (a) DFT Simulation 1280 1290 Frequency (cm-1) 15

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

Theoretical calculations using B 3 LYP/cc-p. VDZ level of theory Vibrational mode DFT Calculated (cm-1) Infrared Intensity (km/mole) 1(σ) 1986 197 2(σ) 1300 37 3(σ) 466 11 4(π) 408 24 5(π) 143 4 ~ 5. 3 times the intensity of the 1279. 6 cm-1 band 17

C 3 • C 6 ~9 peaks/10 cm-1 • sintered rod C 7 Ge. C 3 Ge (a) 35% 13 C/Ge • • C 9 1900 1950 2000 2050 Frequency (cm-1) 18

ν 5 Simultaneous ablation of 5% 13 C and Ge rods ● C 6 1952. 5 (a) C 7 ♦ ♦ ♦ C 6 1936. 7 ν 5 Gen. Cm ? 1928. 3 Ge. C 9 1903. 9 Ge. C 3 ν 1 ? 1918. 9 Ge. CO site ● C 6 natural enrichment single substitutions 1907. 7 Ge. CO ♦ unidentified weak features 1920. 7 Ge. C 3 Ge ν 3 ● ● ♦ ♦ ● Cn ? (b) Ablation of C rod 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 19

▪ 1903. 9 Ge. C 3 ▪ • C 7 ♦ ♦ • ▪ ▲ ν 5 1895. 6, 74 -12 -12 -13 1885. 1, 74 -13 -12 -12 • 1907. 7 Ge 13 CO • • 1876. 4 Ge 13 CO site ν 4 C 6 13 C isotopic shift 1856. 5, 74 -12 -13 -12 ▲ ν 1 1920. 7 Ge. C 3 Ge • ν 3 Ge. C 3 Ge all 13 C isotopic shifts ▪ ν 5 C 7 single 13 C isotopic shifts 1918. 9 Ge. CO site 1907. 7 Ge. CO (b) 5% 13 C and Ge dual ablation ν 3 A (a) DFT Simulation C D 1840 1850 1860 1870 1880 B 1890 1900 1910 1920 20

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

Laser ablation technique vs. Ge. C 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 22

Laser ablation technique vs. Ge. C 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 23

Laser ablation technique vs. Ge. C 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

Conclusions n DFT calculations with B 3 LYP/cc-p. VDZ 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 n 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) n Linear Ge. C 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 25

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