1. HIGH RESOLUTION OVERTONE SPECTROSCOPY OF THE ACETYLENE VAN DER WAALS DIMER, 12 (C 2 H 2 ) 2 K. D IDRICHE, C. L AUZIN, T. F ÖLDES, D. G OLEBOWSKI AND M. H ERMAN International Symposium on Molecular Spectroscopy 66th Meeting June 20-24, 2011 – Ohio State University C. L EFORESTIER Laboratoire de Chimie Quantique et Photophysique Université Libre de Bruxelles Belgium Institut Charles Gerhardt, Monpellier, France

2. FANTASIO+ C ONTINUOUS SUPERSONIC JET FTIR SPECTROMETER MASS SPECTROMETER CW CRDS SET - UP (1.5 µm) Fourier trANsform, Tunable diode and quadrupole mAss spectrometers interfaced to a Supersonic expansIOn Didriche et al., Mol. Phys., 2010, 108, 2155    C 2 H 2 :2CH

3. b a  (10 -6 cm -1 ) wavenumber (cm -1 ) rQ3(J)rQ3(J) rQ2(J)rQ2(J) rQ1(J)rQ1(J) rQ0(J)rQ0(J) pQ1(J)pQ1(J) pQ2(J)pQ2(J) pQ3(J)pQ3(J) pQ4(J)pQ4(J) unit 1 unit 2 b-type simulation (20K) PGOPHER (C. Western, University Of Bristol) Ground State*B state origin (cm-1)06547.58 A (MHz)3528236000 B (MHz)1913.291900 C (MHz)1798.611810  JK (MHZ) 2.334 *Fraser et al., J. Chem. Phys., 1988, 89, 6028 http://pgopher.chm.bris.ac.uk C 2 H 2 (6%)/Ar P 0 = 1.2 atm /slit Didriche et al., Mol. Phys., 2010, 108, 2155 Last year

4. b a  (10 -6 cm -1 ) wavenumber (cm -1 ) rQ3(J)rQ3(J) rQ2(J)rQ2(J) rQ1(J)rQ1(J) rQ0(J)rQ0(J) pQ1(J)pQ1(J) pQ2(J)pQ2(J) pQ3(J)pQ3(J) pQ4(J)pQ4(J) unit 1 unit 2 b-type simulation (20K) PGOPHER (C. Western, University Of Bristol) Ground State*B state origin (cm-1)06547.58 A (MHz)3528236000 B (MHz)1913.291900 C (MHz)1798.611810  JK (MHZ) 2.334 *Fraser et al., J. Chem. Phys., 1988, 89, 6028 http://pgopher.chm.bris.ac.uk C 2 H 2 (6%)/Ar P 0 = 1.2 atm /slit Didriche et al., Mol. Phys., 2010, 108, 2155 further investigation is needed... Last year

5.  = 0°  = 90°  = 180°  = 270° G.T. Fraser et al., J. Chem. Phys. 89 (1988) 6028. 4 equivalent structures Not a rigid rotor !

6. G 16   tun = A 1 + + B 1 + +E + Energy  T UNNELING SPLITTINGS

7. Spectrum Energy 9 1,9 10 1,10 11 1,11 12 1,12 Energy 8 0,8 9 0,9 10 0,10 11 0,11 P(J) lines  ev  tun  rot  ns S TATISTICAL WEIGHTS

8. Spectral analysis

9. 2 - 3 K’ a –K ’’ a 0 - 14 - 32 - 1 S PECTRAL ANALYSIS

10. 0 - 1 Spectrum Energy S PECTRAL ANALYSIS

11. wavenumber T rot = 23 k 0 - 1 S PECTRAL ANALYSIS

12. T rot = 23 k S PECTRAL ANALYSIS 2 - 3 No contribution from E +

13. T rot = 23 k S PECTRAL ANALYSIS 4 - 3

14. Energy 2CH 1CH GS 2200 (MHz) 572 270 Energy  R ESULTS simulationrotational constants for each statetunneling splittings internal rotation is hindered by vibrational excitation

15. b a  (10 -6 cm -1 ) wavenumber (cm -1 ) rQ3(J)rQ3(J) rQ2(J)rQ2(J) rQ1(J)rQ1(J) rQ0(J)rQ0(J) pQ1(J)pQ1(J) pQ2(J)pQ2(J) pQ3(J)pQ3(J) pQ4(J)pQ4(J) unit 1 unit 2 b-type simulation (20K) PGOPHER (C. Western, University Of Bristol) Ground State*B state origin (cm-1)06547.58 A (MHz)3528236000 B (MHz)1913.291900 C (MHz)1798.611810  JK (MHZ) 2.334 *Fraser et al., J. Chem. Phys., 1988, 89, 6028 http://pgopher.chm.bris.ac.uk C 2 H 2 (6%)/Ar P 0 = 1.2 atm /slit F UTUR WORK

16. b a unit 1 unit 2 Ground State*A state origin (cm-1)06538.32 A (MHz)3528235250 B (MHz)1913.291904 C (MHz)1798.611795  JK (MHZ) 2.334 Fraser et al., J. Chem. Phys., 1988, 89, 6028 wavenumber (cm -1 ) a-type simulation PGOPHER (C. Western, University Of Bristol) http://pgopher.chm.bris.ac.uk a-type simulation + b-type simulation 2 CH stretches F UTUR WORK

17. A CKNOWLEDGEMENTS X. de Ghellinck Athéna Rizopoulos Patrick Van Poucke Baris Kizil Darius Golebiowski Fundings: -FNRS -ULB -Action de Recherches Concertées de la Communauté française de Belgique

19. J even, I H = 0 A1±A1± I H = 0 ; g I = 1 J even, I H = 0J odd, I H = 1 E±E± I H = 1 ; g I = 3 J odd, I H = 1J even, I H = 0 A2±A2± I H = 1 ; g I = 3 J odd, I H = 1 B2±B2± I H = 0,2 ; g I = 6 12 C 2 H 2 + 12 C 2 H 2  evrt NS G.T. Fraser et al., J. Chem. Phys. 89 (1988) 6028. Results