Millimiter-wave spectroscopy of OSSO

Transcription

1 Millimiter-wave spectroscopy of OSSO Marie-Aline Martin-Drumel a,1, Jennifer van Wijngaarden b, Oliver Zingsheim a, Sven Thorwirth a, Frank Lewen a & Stephan Schlemmer a a I. Physikalisches Institut, Universität zu Köln, Cologne, Germany b Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada ISMS 69 th meeting June 16, Present address: Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

2 Sulfur-Rich Oxides S n O m Sulfur: element with the largest number of binary oxides 1 Lower oxides of sulfur: SO, S 2 O, S 2 O 2, S 3 O... Sulfur containing species in space: 10 % of known interstellar molecules Detected sulfur oxides: SO 2 2, SO 3 Observed in molecular clouds, star forming regions, atmospheres (Venus 4, Io) 1 R. Steudel, Top Curr Chem 231, 203 (2003) 2 L. E. Snyder, Astrophys. J. 198, L81(1975) 3 C. A. Gottlieb & J. A. Ball, Astrophys. J. 184, L59 (1973) 4 Image: NASA, 2

3 Structural complexity of sulfur oxides Example: S 4 O 1 11 stable conformers B3LYP/6-31G(2df) Energy within 120 kj/mol 1 M. W. Wong et al., Chem. Eur. J. 13, 502 (2007) 3

4 Disulfur Dioxide, S 2 O 2 branched cis trans µ = 1.31 D 1 µ = 3.17 (10) D 2 µ = 0 D E(branched) < E(cis) E(trans) 1 1 Calculation: CCSD(T)/cc-pwCVQZ 2 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 4

5 Disulfur Dioxide, S 2 O 2 branched cis trans µ = 1.31 D 1 µ = 3.17 (10) D 2 µ = 0 D E(branched) < E(cis) E(trans) 1 Only the cis isomer have been observed to date 2 1 Calculation: CCSD(T)/cc-pwCVQZ 2 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 4

6 Spectroscopy of OSSO b planar, C 2v symmetry b-type transitions only levels with K a K c = ee/oo are populated 1 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 2 S. Thorwirth et al., J. Mol. Struct. 795, 219 (2006) 5

7 Spectroscopy of OSSO b planar, C 2v symmetry b-type transitions only levels with K a K c = ee/oo are populated Previous investigations: Pure rotational spectroscopy up to 50 GHz 1,2 Produced by discharge in SO 2 OSSO (ν = 0, ν 3 = 1) O 34 SSO (ν = 0) 1 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 2 S. Thorwirth et al., J. Mol. Struct. 795, 219 (2006) 5

8 Experimental set-up Submillimeter spectrometer at Uni-Köln Frequency multiplication chain (70 GHz 1.1 THz) 5 m long absorption cell Radio-frequency (RF) discharge 6

9 Electronic configuration Schottky Detector Bias Box RF Oscillator + Discharge Cell Frequency Tripler 3 Pre-Amplifier Gain Power Supply 10 V / 0.3 A Overvoltage Control unit µw-amplifier Lock-in Osc. Out FM input Synthesizer Coaxial cable Amplifier IEEE/USB Converter 100kHz 43.5GHz Oscilloscope Computer (Labview) Rubidium Reference Frequency (10 MHz) 7

10 Optical arrangement Rooftop Mirror RF Resonator HDPE Lens 45 Frequency Multipler Rotation (45 ) Polarizer Vertical polarization Horizontal polarization Schottky Detector Standard gain Antenna 10 m absorption length 8

11 RF-discharge 45 Precursor Needle Valve Fine Tuning RF Generator Turbomolecular Pump 10 cm Cold Trap Pressure Gauge Hole Mass Spek. RF Resonator 5 m Precursor: SO 2 Discharge power: 5W Pressure: 3 µbar (flow) Teflon Window Other observed species: SO 2 (GS, ν 3 = 1), SO 18 O, SO 17 O, S 2 O, SO, 34 SO, 33 SO, S 18 O 9

12 Experimental conditions Frequency range covered: GHz (steps 10 khz) GHz (steps 50 khz) 20 ms time constant Second harmonic detection 10

13 OSSO: ground and ν 3 = 1 states Intensity /mv S 2 O OSSO, = 0 OSSO, 3 = Frequency /GHz 11

14 Results 608 lines in the ground state (J 95, K a 24) GHz, GHz 156 lines in ν 3 = 1 (J 54, K a 12) GHz 12

15 Results 608 lines in the ground state (J 95, K a 24) GHz, GHz 156 lines in ν 3 = 1 (J 54, K a 12) GHz SNR up to 130, unc. down to 5 khz 12

16 Results 608 lines in the ground state (J 95, K a 24) GHz, GHz 156 lines in ν 3 = 1 (J 54, K a 12) GHz SNR up to 130, unc. down to 5 khz fc-ccsd(t)/cc-pv(q+d)z calculation: Vibrationally excited transitions assigned to the ν 3 mode 131 cm 1 (calc.) 12

17 Frequency and uncertainty Pseudo-Voigt profile of type (1 s)g + sl: ( ) 2 ν B y(ν) = A (1 s)exp ln 2 +s C 1 1+ ( ν B C A height of the line, B center frequency, C FWHM, s shape ) 2 Uncertainty on line frequency 1 : δ(ν) = (C ν)1/2 SNR { (1 s) ( ) 2 1/4 + s π ln 2 ( ) 32 1/2 } π 1 D. Landman et al., Astrophys. J. 261, 732 (1982) 13

18 Frequency and uncertainty 14

19 Frequency and uncertainty 15

20 Fits Watson-A reduction with SPFIT/SPCAT programs 1 GS 74 lines literature 2,3 608 lines this work ν 3 = 1 20 lines literature lines this work 1 H. M. Pickett, J. Mol. Spectrosc. 148, 371 (1991) 2 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 3 S. Thorwirth et al., J. Mol. Struct. 795, 219 (2006) 16

21 Fits Watson-A reduction with SPFIT/SPCAT programs 1 GS 74 lines literature 2,3 608 lines this work RMS= 40 khz (our data: 23 khz) σ = 0.99 ν 3 = 1 20 lines literature lines this work RMS= 50 khz (our data: 7 khz) σ = H. M. Pickett, J. Mol. Spectrosc. 148, 371 (1991) 2 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 3 S. Thorwirth et al., J. Mol. Struct. 795, 219 (2006) 16

22 Molecular parameters: GS and ν 3 = 1 Parameter ν = 0 ν 3 = 1 (MHz) This work S. Thorwirth (2006) This work F. J. Lovas (1974) A (10) (72) (45) (22) B (34) (33) (77) (62) C (31) (20) (72) (77) J (20) (44) (79) (45) JK (14) (35) (13) (39) K (57) (38) (15) 98.7 (46) δ J (72) (17) (25) (80) δ K (27) (83) (87) 6.21 (39) Φ J (49) 13.9 (24) Φ JK (12) (30) (17) Φ KJ (48) (15) (31) Φ K (16) 3.51 (43) 6.74 (37) φ J (23) (11) (19) φ JK (10) (14) φ K (25) (32) L J (43) L JJK (18) L JK (46) L KKJ (14) (17) L K (15) 7.7 (18) l J (22) l JK (12) l KJ (37) l K (58) 17

23 Molecular parameters: GS and ν 3 = 1 Parameter ν = 0 ν 3 = 1 (MHz) This work S. Thorwirth (2006) This work F. J. Lovas (1974) A (10) (72) (45) (22) B (34) (33) (77) (62) C (31) (20) (72) (77) J (20) (44) (79) (45) JK (14) (35) (13) (39) K (57) (38) (15) 98.7 (46) δ J (72) (17) (25) (80) δ K (27) (83) (87) 6.21 (39) Φ J (49) 13.9 (24) Φ JK (12) (30) (17) Φ KJ (48) (15) (31) Φ K (16) 3.51 (43) 6.74 (37) φ J (23) (11) (19) φ JK (10) (14) φ K (25) (32) L J (43) L JJK (18) L JK (46) L KKJ (14) (17) L K (15) 7.7 (18) l J (22) l JK (12) l KJ (37) l K (58) 17

24 Molecular parameters: GS and ν 3 = 1 Parameter ν = 0 ν 3 = 1 (MHz) This work S. Thorwirth (2006) This work F. J. Lovas (1974) A (10) (72) (45) (22) B (34) (33) (77) (62) C (31) (20) (72) (77) J (20) (44) (79) (45) JK (14) (35) (13) (39) K (57) (38) (15) 98.7 (46) δ J (72) (17) (25) (80) δ K (27) (83) (87) 6.21 (39) Φ J (49) 13.9 (24) Φ JK (12) (30) (17) Φ KJ (48) (15) (31) Φ K (16) 3.51 (43) 6.74 (37) φ J (23) (11) (19) φ JK (10) (14) φ K (25) (32) L J (43) L JJK (18) L JK (46) L KKJ (14) (17) L K (15) 7.7 (18) l J (22) l JK (12) l KJ (37) l K (58) 17

25 Molecular parameters: GS and ν 3 = 1 Parameter ν = 0 ν 3 = 1 (MHz) This work S. Thorwirth (2006) This work F. J. Lovas (1974) A (10) (72) (45) (22) B (34) (33) (77) (62) C (31) (20) (72) (77) J (20) (44) (79) (45) JK (14) (35) (13) (39) K (57) (38) (15) 98.7 (46) δ J (72) (17) (25) (80) δ K (27) (83) (87) 6.21 (39) Φ J (49) 13.9 (24) Φ JK (12) (30) (17) Φ KJ (48) (15) (31) Φ K (16) 3.51 (43) 6.74 (37) φ J (23) (11) (19) φ JK (10) (14) φ K (25) (32) L J (43) L JJK (18) L JK (46) L KKJ (14) (17) L K (15) 7.7 (18) l J (22) l JK (12) l KJ (37) l K (58) 17

26 O 34 SSO SO 18 O Intensity /mv u-line -0.2 O 34 SSO, = Frequency /GHz 18

27 Fit Watson-A reduction with SPFIT/SPCAT programs 1 19 lines literature 2 58 lines this work ( GHz) RMS= 72 khz (our data: 17 khz) σ = H. M. Pickett, J. Mol. Spectrosc. 148, 371 (1991) 2 F. J. Lovas et al., J. Chem. Phys. 60, 5005 (1974) 19

28 Molecular parameters of O 34 SSO Parameter This work F. J. Lovas (1974) A (42) (28) B (65) (16) C (62) (13) J (89) (96) JK (62) (44) K (14) 89.8 (60) δ J (86) (97) δ K (43) 5.85 (43) Φ JK (56) Φ KJ (22) Φ K (24) 20

29 Molecular parameters of O 34 SSO Parameter This work F. J. Lovas (1974) A (42) (28) B (65) (16) C (62) (13) J (89) (96) JK (62) (44) K (14) 89.8 (60) δ J (86) (97) δ K (43) 5.85 (43) Φ JK (56) Φ KJ (22) Φ K (24) 20

30 Geometry of OSSO (6) Å Å 2.011(3) Å 112.7(5) (1) 1.458(2) Å Å 1.467(2) Å Empirical, F. J. Lovas et al. (1974) Calculated, CCSD(T)/cc-pwCVQZ Empirical, this work, using zero-point vibrational corrections calculated at CCSD(T)/cc-pV(Q+d)Z 21

31 Geometry of OSSO S-S bond length: about 7 % shorter than in isovalent S S. Thorwirth et al., J. Chem. Phys. 123, (2005) Å 22

32 Prospects cis-osso Improved structure other isotopologues (FTMW) ν 3 band center: beamtime accepted at SOLEIL synchrotron 23

33 Prospects cis-osso Improved structure other isotopologues (FTMW) ν 3 band center: beamtime accepted at SOLEIL synchrotron branched-s 2 O 2 Pure rotation Chirped-pulse + FTMW (see talk RE03) HR ro-vibration (SOLEIL) 23

34 Prospects cis-osso Improved structure other isotopologues (FTMW) ν 3 band center: beamtime accepted at SOLEIL synchrotron branched-s 2 O 2 Pure rotation Chirped-pulse + FTMW (see talk RE03) HR ro-vibration (SOLEIL) trans-osso (µ = 0) HR ro-vibration (SOLEIL) 23

35 Other lower oxides of sulfur 24

36 Acknowledgements Research funding: DFG SFB 956, DFG TH 1301/3-2 25