Transcript CF4
HIGH RESOLUTION STIMULATED RAMAN SPECTROSCOPY OF CARBON TETRAFLUORIDE CF4 V. BOUDON, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, 9. Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France D. BERMEJO, R. Z. MARTÍNEZ, Instituto de Estructura de la Materia, CSIC Serrano 123, E-28006 Madrid, Spain 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Contents I. The CF4 molecule II. Raman experiment III. The ν1 and 2ν1–ν1 bands IV. The ν2, 2ν2 and 3ν2–ν2 bands V. Conclusions and perspectives 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 I. The CF4 molecule 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Carbon tetrafluoride (CF4) CF4 is a strong greenhouse gas (natural and anthropogenic origin) Global Warming Potential = 6500 (CO2 = 1), lifetime = 50,000 years Concentration = 75 pptv, annual increase = 1.6 % Point group Td ν1 ν2 ν3 ν4 A1 E F2 F2 Stretching Bending Stretching Bending Raman Raman IR IR 909 cm-1 435 cm-1 1283 cm-1 631 cm-1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 CF4 vibrational levels 2ν1–ν1 Coriolis INFRARED Boudon et al., Mol. Phys. 109, 2273–2290 (2011) RAMAN: This work Global analysis 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Theoretical model – Tensorial formalism Systematic expansion of effective Hamiltonian and transition moment up to any order and for any polyad scheme, thanks to group theory and tensorial methods H Pk t K,n v v' ss ' all indexes K,n v v' (A1g ) R Vss ' Parameters Rotation Vibration All interactions are automatically included Vibrational extrapolation Global analyses 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 II. Raman experiment 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Experimental setup in Madrid Inverse Raman Spectrometer 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The spectra 135 K ν1, ν2, 2ν2 296 K ν1, 2ν1–ν1, 2ν2, 3ν2–ν2 350 K ν1, ν1+ν2–ν4 Spectral resolution : ca. 0.003 cm–1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 III. The ν1 and 2ν1–ν1 bands 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 2ν1 hot band at 135 K 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 2ν1-ν1 hot band at room temperature 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Fit residuals for line positions 232 assignments Jmax = 73 St. Dev. = 2.868 dRMS = 0.632 10-3 cm-1 2304 assignments Jmax = 76 St. Dev. = 2.741 dRMS = 0.471 10-3 cm-1 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 IV. The ν2, 2ν2 and 3ν2–ν2 bands 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The ν2 band at 134 K 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The ν2 band at 134 K (details & residuals) Part of OP branch Q branch Part of RS branch 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 2ν2 band (A1 sublevel) at 135 K 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The 3ν2-ν2 hot band at room temperature Extrapolation from 2ν2 and ν2 Anharmonicity was adjusted manually 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 IV. Conclusions and perspectives 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 The CF4 equilibrium bond length 4 di Be B0 Bi 2 i 1 with Bi Bi B0 i 3h re 64 2 cM F Be Using present Raman data for ν1 and ν2 and infrared results from Boudon et al., Mol. Phys. 109, 2273–2290 (2011) for ν3 and ν4 , we get: re 1.315880(53) Å Ab initio value from Wang et al., J. Chem. Phys. 112, 1353– 1366 (2000): re 1.31526 Å 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012 Perspectives for CF4 spectroscopy • Analysis of new IR spectra: ν1+ν2, ν1+ν4 • Analysis of Raman hot bands: ν1+ν2–ν2, ν1+ν4–ν4 • ν3 and 2ν4 being linked through Coriolis interaction, global analysis of all IR and Raman bands in the 0–1600 cm–1 region • Study of hot bands in the ν3 region for atmospheric applications • Measurements and analysis of IR intensities or crosssections 67th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2012