1. ABSOLUTE 17 O NMR SCALE: a JOINT ROTATIONAL SPECTROSCOPY and QUANTUM-CHEMISTRY STUDY Cristina PUZZARINI and Gabriele CAZZOLI Dipartimento di Chimica “G. Ciamician”, Università di Bologna Michael E. HARDING and Jürgen GAUSS Institut für Physikalische Chemie, University of Mainz Columbus — June 26, 2009

2. 1) Experiment: Instrument & Technique Instrument & Technique

3. FREQUENCY RANGE covered @ LMSB (2) 50-600 GHz (from fundamental to the 6th harmonic) + 600-800 GHz (8th harmonic) + 600-800 GHz (8th harmonic) (3) 1.0-1.2 THz (9th harmonic) + 1.33-1.6 THz (12th harmonic) + 1.33-1.6 THz (12th harmonic) (1) 8-120 GHz (wave-guide Stark cell – P band)

4. MILLIMETER-WAVE EXPERIMENTAL SET-UP (2) BLOCK DIAGRAM OF THE 50-800 GHz SPECTROMETER SYNTH 10 kHz-1 GHz MULT fSfS nfSnfS MIX MULT SYNCR ref: 20 MHz RF OSCILL 3.7- 7.6 GHz f RF 20 MHz 90 MHz |f G - mf RF | GUNN P. SUPPLY and SYNCR ref: 73 MHz |f RF - nf S | HP8642A SYNTH MIX corr fGfG fGfG MULTIPLIER InSb DETECTOR PREAMPL LOCK - IN 10 MHz freq. standard 1.666 kHz ref GUNN DIODES THERMOSTAT or liquid N 2 system

5. Measurements: Lamb-dip technique Corner cube mirror Cell InSb detector Polarizer Frequency modulated source Scheme of the radiation path Using free-space cell G. Cazzoli & L. Dore, J. Mol. Spectrosc. 143, 231 (1990).

6. 1) Partial saturation 2) Only Doppler profile 3) Rad: back and forward Measurements: Lamb-dip technique + v za - v za vz= 0vz= 0vz= 0vz= 0

7.  ( ) Lamb-dip effect

8. Measurements: Lamb-dip technique CH 2 BrF Doppler Lamb-dip the Lamb-dip technique allows 1) To well resolve hfs ( /  = 3.9x10 7,  =16 kHz) 2) To accurately determine - frequencies - frequencies - hfs parameters - hfs parameters

9. GHOST TRANSITIONS

10. 2) Theory: Computational details & Computational details & requirements requirements

11. Parameters of Rotational Spectroscopy Effective Hamiltonian: determination of H Rot via quantum chemistry Rotational Hamiltonian Rotational constants Nuclear quadrupole coupling constants Spin-rotation interactions Spin-spin (direct) interactions interactions

12. Quantum-Chemical Calculation of Spectroscopic Parameters Nuclear quadrupole coupling Nuclear quadrupole coupling first-order property: requires first derivatives of energy Spin-rotation interaction Spin-rotation interaction second-order property: requires second derivatives of energy ELECTRIC FIELD GRADIENT

13. requires equilibrium geometry: no „electronic property“ addditional contribution due to:  indirect spin-spin coupling (usually negligible) Quantum-Chemical Calculation of Spectroscopic Parameters Spin-spin coupling Spin-spin coupling DIPOLAR SPIN-SPIN COUPLING TENSOR  vibrational corrections (anharmonic force field)

14. Beyond the Rigid-Rotator Approximation COUPLING of ROTATIONAL and VIBRATIONAL MOTION  Vibrational corrections to properties: PERTURBATION THEORY starting from the rigid-rotator harmonic oscillator approximation the rigid-rotator harmonic oscillator approximation Vibrational corrections require: anharmonic force field calculations anharmonic force field calculations

15. Accurate hyperfine parameters >>>> Main requirements : - accurate method - cc basis set - CV corrections

16. Accurate hyperfine parameters >>>> Main requirements : - accurate method [CCSD(T)] - cc basis set [n  Q] - CV corrections [additivity/CV bases]

17. Accurate hyperfine parameters >>>> Main requirements : - accurate method [CCSD(T)] - cc basis set [n  Q] - CV corrections [additivity/CV bases] - vibrational corrections

18. Accurate hyperfine parameters >>>> Main requirements : - accurate method [CCSD(T)] - cc basis set [n  Q] - CV corrections [additivity/CV bases] - vibrational corrections [ff: -correlated method method -basis: n  T] -basis: n  T]

19. 3) Results 3) Results

20. Lamb-dip spectra recorded Hyperfine parameters computed Spectra analysis & assignment

21. Para lines Para lines (I H,tot = 0) hfs: only 17 O

22. Hyperfine parameters ………. 17 O: -nuclear quadrupole coupling -spin-rotation H: H: —

25. Ortho lines Ortho lines (I H,tot = 1) hfs: 17 O + H

26. Hyperfine parameters ………. 17 O: -nuclear quadrupole coupling -spin-rotation -spin-spin ( 17 O-H) H: H: -spin-rotation -spin-spin (H-H)

28. J = 1 1,0 – 1 0,1

31. 17 O ExperimentTheory C aa -28.86(11)-28.18-28.61 C bb -27.229(81)-27.94-27.99 C cc -18.422(54)-18.46-18.49 Results ……. results in kHz

32. Method:CCSD(T)Equil. (exp r e ) Vib. Corr. (VPT2) (DVR)Total(Eq+Vib) basis basisaugCV6ZaugCV5ZaugCV5Z C aa C aa-22.251-5.933-6.361-28.184-28.612 C bb C bb-25.196-2.741 -2.794 -2.794 -27.937-27.990 C cc C cc-17.476-0.988 -1.015 -1.015 -18.464-18.491

33. „Experimental“ Determination of Absolute Shieldings measure rotational spectrum extract nuclear spin-rotation constant subtract rovibrational corrections convert to paramagnetic shielding add calculated diamagnetic shielding add rovibrational corrections consider temperature effects  experiment  C v,J  C e  σ e para  σ e dia  σ v,J  σ(T)

34. Results …… Absolute 17 O NMR scale [ppm] [ppm]isotropic  (dia) calculated 416.4  (para) from exp -78.5  (equil)  (vib)  (T) -338.1(3)-11.7-0.4  (300K) 326.2(3) Best theoretical estimate 325.6 ppm

35. Results …… the other hf parameters [MHz/kHz] [MHz/kHz]ExperimentTheory 1.5  aa ( 17 O) -13.3060(25) -13.21 MHz -13.21 MHz (  bb -  cc )/4 ( 17 O) -2.88509(52) -2.85 MHz -2.85 MHz 1.5D aa ( 17 O-H) 23.44(43) 23.64 kHz 23.64 kHz (D bb -D cc )/4 ( 17 O-H) 5.182(97) 5.11 kHz 5.11 kHz 1.5D aa (H-H) -101.8(25) -102.27 kHz C aa (H) -34.63(30) -34.27 kHz -34.27 kHz C bb (H) -30.78(25) -31.16 kHz -31.16 kHz C cc (H) -32.91(12) -32.54 kHz -32.54 kHz

36. Calculations performed using C FOUR : http://www.cfour.de THANK YOU for your attention!! THANK YOU for your attention!!

41. NMRMW Bryce & Wasylishen, Acc. Chem. Res. 36, 327 (2003) connection nuclear magnetic shielding  absolute shielding scales Ramsey-Flygareequations form of Hamiltonians: coupling mechanism vs tensor rank nuclear quadrupole coupling  nuclear quadrupole coupling C Q nuclearspin-rotationCchemicalshift tensor spin-spin coupling (rank 2) C 3 scalar spin-spin coupling (rank 0) C 4 direct dipolar couplingD indirect spin-spin couplingJ

42. Frerking, Langer, J. Chem. Phys. 74, 6990 (1981) Radioastronomical study (Bok globule B335) Absolute 17 O NMR Scale OLD

43. C( 17 O)-30.4(12)  C(vib) -0.1  (para) -483.7(172)  (dia) 445.1  (eq) -38.7(172)  (vib) -5.73  (T) -0.35  (300K) -44.8(172) Wasylishen et al., JCP 84, 1057 (1984); Sundholm, Gauss, Schäfer JCP 105, 11051 (1996) Best theoretical estimate -59.34 ppm OLD

44. Cazzoli, Dore, Puzzarini, Beninati, Phys. Chem. Chem. Phys. 4, 3575 (2002) New laboratory study using Lamb-dip technique Absolute 17 O NMR Scale NEW

45. C( 17 O)-30.4(12)-31.61(4)  C(vib) -0.1  (para) -483.7(172)-501.8(6)  (dia) 445.1  (eq) -38.7(172)-56.7(6)  (vib) -5.73  (T) -0.35  (300K) -44.8(172)-62.7(6) Wasylishen et al., JCP 84, 1057 (1984); Sundholm, Gauss, Schäfer JCP 105, 11051 (1996) Best theoretical estimate -59.34 ppm OLDNEW