1 / 26

Infrared Observation of the ν 1 (  ) and ν 2 (  ) Stretching Modes of Linear GeC 3

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

jerrod
Download Presentation

Infrared Observation of the ν 1 (  ) and ν 2 (  ) Stretching Modes of Linear GeC 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Infrared Observation of the ν1() and ν2()Stretching Modes of Linear GeC3 E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham Department of Physics and Astronomy Texas Christian University Fort Worth, TX 76129 63rd 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 GeC3 molecule that had not been observed when GeC3Ge and GeC3Si were discovered (Robbins et al, JCP. 2001,2002) • Identify structure via isotopic shift measurements and assign the vibrational fundamentals

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

  4. Previous Work • Germanium carbon clusters • Linear GeC3Ge was previously produced by dual laser ablation of germanium and carbon rods. The ν3(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)

  5. Previous Work • In later work using single laser ablation of a sintered germanium-carbon rod the yield of GeC3Ge was improved allowing the observation of the next most intense infrared active modes • The ν4(u) stretching mode was assigned to 735.3 cm-1 (74-12-12-12-74) and the bending mode ν6(πu) was assigned to 580.1cm-1(to be published)

  6. The ν4(u) stretching mode of linear GeC3Ge (to be published) 736.0 74-12-12-12-72 735.3 74-12-12-12-74 76-12-12-12-72 736.7 74-12-12-12-70 72-12-12-12-72 737.5 72-12-12-12-70, 734.5 76-12-12-12-74 738.3 70-12-12-12-70, Ge/12C rod Simulation 720 725 730 735 740 745 750 Frequency (cm-1)

  7. Previous Work • Germanium, carbon, and silicon mixed cluster • Linear GeC3Si was previously produced by dual laser ablation of Ge/C and Si/C rods. The ν1() 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 GeC3Si was improved. The ν4() stretching mode and the bending mode ν6(π) are tentatively assigned at 824.7 cm-1 and 590.5 cm-1. 13C isotopic data are required to confirm the assignments

  8. The “ν4()” stretching mode of linear GeC3Si 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)

  9. GeC3Si (B3LYP/cc-pVDZ) 1279.6 Linear GeC3 or SiC3 ? 1277.1 1257.0 1254.5 (a) 20% 13C/Ge/Si sintered rod 1220 1230 1240 1250 1260 1270 1280 1290 Frequency (cm-1)

  10. Linear GeC3 1279.6 (a) 35% 13C/Ge sintered rod 1257.0 1257.0 1257.0 1257.0 1277.1 1277.1 1277.1 1254.5 1254.5 1254.5 1254.5 1230.2 1230.2 1230.2 1230.2 1230.2 1230.2 1232.7 1232.7 1232.7 1232.7 1232.7 1232.7 1252.7 1252.7 1252.7 1252.7 1252.7 1220 1230 1240 1250 1260 1270 1280 1290 Frequency (cm-1)

  11. GeC3 isomers (Leszczynski et al. J. Chem. Phys. 2005) kite 0 kcal/mol MP2 (CCSD) [DFT] fan +2.1 kcal/mol kJ/mol linear +9.2 kcal/mol kJ/mol

  12. Theoretical calculations using B3LYP/cc-pVDZ level of theory Vibrational mode DFT Calculated (cm-1) Infrared Intensity (km/mole) 1(a1) 1409 155 2(a1) 921 28 3(a1) 505 40 4(b1) 192 11 5(b2) 1011 3 6(b2) 323 31 kite +11.1 kcal/mol

  13. Theoretical calculations using B3LYP/cc-pVDZ level of theory Vibrational mode DFT Calculated (cm-1) Infrared Intensity (km/mole) 1(a1) 1136 4 2(a1) 696 29 3(a1) 393 19 4(b1) 217 40 5(b2) 1623 84 6(b2) 313 4 fan +7.4 kcal/mol

  14. Theoretical calculations using B3LYP/cc-pVDZ 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 linear 0 kcal/mol

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

  16. The ν2(σ) mode of linear GeC3 aDFT calculations scaled by two scaling parameters function (R. H. Kranze et al. ,JCP 1995) :

  17. Theoretical calculations using B3LYP/cc-pVDZ 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

  18. C3 1900 1950 2000 2050 •C6  ~9 peaks/10 cm-1 • (a) 35% 13C/Ge sintered rod • GeC3Ge  •  C9 C7  Frequency (cm-1)

  19. ν5 • Simultaneous ablation • of 5% 13C and Ge rods ● C6 1952.5 ν3 GeC3Ge GenCm ? ♦ unidentified weak features 1920.7 GeCO site GeC9 ● C6 natural enrichment single substitutions ν1 ? C6- GeCO GeC3 1928.3 1936.7 1918.9 ν5 1907.7 C7 1903.9 ● ♦ ♦ ● ● ♦ ♦ ♦ Cn? (b) Ablation of C rod 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970

  20. ν3 1895.6, 74-12-12-13 1885.1, 74-13-12-12 1856.5, 74-12-13-12 GeCO site (b) 5% 13C and Ge dual ablation GeC3Ge GeCO • ν3GeC3Ge all 13C isotopic shifts 1907.7 1918.9 ▪ ν5C7 single 13C isotopic shifts 1920.7 ν1 ▲ν4C613C isotopic shift GeC3 Ge13CO site ν5 C7 1903.9 Ge13CO • ♦ 1876.4 ♦ • 1907.7 ▪ ♦ ▪ • ▪ • ♦ ▲ • A (a) DFT Simulation C B D 1840 1850 1860 1870 1880 1890 1900 1910 1920

  21. The ν1(σ) mode of linear GeC3 aDFT calculations scaled by one scaling parameter :

  22. Laser ablation technique vs. GeC3 isomers convergence initial geometry • We have experimental evidence that the laser ablation • technique produces similar to Knudsen evaporation • cell evaporation (Drowart et al., JCP 1959) • 10% C2 • 30% C1 • 60% C3

  23. Laser ablation technique vs. GeC3 isomers initial geometry • We have experimental evidence that the laser ablation • technique produces similar to Knudsen evaporation • cell evaporation (Drowart et al., JCP 1959) • 10% C2 • 30% C1 • 60% C3 convergence

  24. Laser ablation technique vs. GeC3 isomers convergence initial geometry • We have experimental evidence that the laser ablation • technique produces similar to Knudsen evaporation • cell evaporation (Drowart et al., JCP 1959) • 10% C2 • 30% C1 • 60% C3

  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 MC3 (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 GeC3 was formed by the laser ablation technique. The ν1(σ) and ν2(σ) stretching modes have been observed at 1903.9 and 1279.6 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)

More Related