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G. Cazzoli, C. Puzzarini Dipartimento di Chimica “G. Ciamician”, Università di Bologna G. Buffa

Pressure-broadening of water lines in the THz frequency region: improvements and confirmations for spectroscopic databases. G. Cazzoli, C. Puzzarini Dipartimento di Chimica “G. Ciamician”, Università di Bologna G. Buffa IPCF-CNR and Dipartimento di Fisica "E. Fermi", Pisa.

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G. Cazzoli, C. Puzzarini Dipartimento di Chimica “G. Ciamician”, Università di Bologna G. Buffa

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  1. Pressure-broadening of water lines in the THz frequency region: improvements and confirmations for spectroscopic databases G. Cazzoli, C. Puzzarini Dipartimento di Chimica “G. Ciamician”, Università di Bologna G. Buffa IPCF-CNR and Dipartimento di Fisica "E. Fermi", Pisa 10th International HITRAN Conference — 22-24 June, 2008

  2. 1) Experimental details: The THz spectrometer 1) Experimental set-up: The THz spectrometer 2) Theoretical calculations: The semiclassical approach 2) Theoretical calculations: The semiclassical approach 3) Experiment & Theory: Results 3) Experiment & Theory: Results OUTLINES

  3. 1) Experimental details: The THz spectrometer - set up - techniques - procedure 1) Experimental details: The THz spectrometer - set up - techniques - procedure

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

  5. CHOPPER GUNN DIODES MULTIPLIER Ge DETECTOR CELL fG PREAMPL GUNN P. SUPPLY and SYNCR ref: 73 MHz MIX MULT ref HP8642A SYNTH 73 MHz |fG - mfRF | 300 Hz LOCK-IN AMPLIFIER  RF OSCILL 3.7- 7.6 GHz fRF FUNCTION GENERATOR corr SYNCR ref: 20 MHz 20 MHz MIX |fRF - nfS| 10 MHz freq. standard nfS SYNTH 10 kHz-1 GHz MULT fS BLOCK DIAGRAM of the 1.0-1-6 THz SPECTROMETER 2x frequency modualtion FREQUENCY MODULATION TECHNIQUE

  6. CHOPPER GUNN DIODES MULTIPLIER Ge DETECTOR CELL fG PREAMPL GUNN P. SUPPLY and SYNCR ref: 73 MHz MIX MULT ref HP8642A SYNTH 73 MHz |fG - mfRF | 300 Hz LOCK-IN AMPLIFIER  RF OSCILL 3.7- 7.6 GHz fRF FUNCTION GENERATOR corr SYNCR ref: 20 MHz 20 MHz MIX |fRF - nfS| 10 MHz freq. standard nfS SYNTH 10 kHz-1 GHz MULT fS BLOCK DIAGRAM of the 1.0-1-6 THz SPECTROMETER chopper frequency revolution AMPLITUDE MODULATION TECHNIQUE

  7. (3) EXPERIMENTAL SET-UP in the THz REGION The 1.0-1.6 THz SPECTROMETER Bolometer Chopper Quartz cell (1cm long) THz scource (gunn + multiplier)

  8. (3) EXPERIMENTAL SET-UP in the THz REGION The 1.0-1.2 THz SPECTROMETER THz scource Cell

  9. 1) Experimental details: The THz spectrometer - set up - techniques - procedure 1) Experimental details: The THz spectrometer - set up - techniques - procedure

  10. AMPLITUDE MODULATION TECHNIQUE Natural line profile Lambert-Beer law I = I0 exp[(-0)L]

  11. LINE SHAPE ANALYSIS To retrieve COLLISIONAL HALF-WIDTH L: by fitting the observed line profiles – natural line profiles - directly to the chosen line profile model (Voigt profile, Galatry profile, Speed Dependent Voigt profile, … …) Residuals: Obs. – Calc.

  12. a2 () = 2/K(x,y,z) cos 2 d  0 SOURCE MODULATION TECHNIQUE FREQUENCY MODULATION (sine wave): (t) = ( - 0) +  cos mt =modulation depth m=modulation frequency Validity: Absorption  6% I = I0 [1- (-0)L] Line profile expanded in a cosine Fourier series. 2nd harmonic detection: K(x, y, z) = Voigt, Galatry or SP-Voigt or … function

  13. LINE SHAPE ANALYSIS COLLISIONAL HALF-WIDTH L: by fitting the observed line profiles to a model that explicitly accounts for frequency modulation [Cazzoli & Dore JMS141, 49 (1990); Dore JMS221, 93 (2003)]. Residuals: Obs. – Calc.

  14. 1) Experimental details: The THz spectrometer - set up - techniques - procedure 1) Experimental details: The THz spectrometer - set up - techniques - procedure

  15. LINE SHAPE ANALYSIS:Which line profile model? LINE SHAPE ANALYSIS:Which line profile model? Galatry profile Voigt profile The 301.8 GHz line of O3 broadened by N2

  16. LINE SHAPE ANALYSIS:Which line profile model? LINE SHAPE ANALYSIS:Which line profile model? Galatry vs Speed-dependent Voigt profile

  17. RETRIEVAL PARAMETERS PRESSURE BROADENING COEFFICIENT : by a weightedlinear fit of L against P L =0 + perturb  Pperturb Lorentzian halfwidth perturb Broadening due to absorber 0

  18. RETRIEVAL PARAMETERS PRESSURE SHIFT COEFFICIENT s: by a weightedlinear fit of  against P =0 + sperturb  Pperturb Transition frequency s Frequency at Ppertub = 0 0

  19. 2) Theoretical calculations: The semiclassical approach 2) Theoretical calculations: The semiclassical approach

  20. THEORETICAL DETAILS COLLISIONAL RELAXATION described within the IMPACT APPROXIMATION by the EFFICIENCY FUNCTION P. For a line ifP = 1 - < i | S | i ><f | St | f > S = scattering matrix, H0 = Hamiltonian of internal degrees, V = collisional interaction, O = time ordering operator. SEMICLASSICAL APPROXIMATION (impact parameter b, relative velocity v, internal state of perturber r): P = P(b,v,r). The linewidth  and lineshift s: real and imaginary parts of P: r = population of level r, f(v) = Maxwellian velocity distribution, n = perturber density.

  21. 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: detailed comparison 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: detailed comparison

  22. H2O: THz pure rotational lines investigated J = 31,2 - 30,3* (1.097 THz) J = 11,1 - 00,0 (1.113 THz) J = 72,5 - 81,8 (1.147 THz) J = 31,2 - 22,1* (1.153 THz) J = 63,4 - 54,1* (1.158 THz) J = 32,1 - 31,2* (1.163 THz) J = 85,4 - 76,1 (1.168 THz) J = 74,4 - 65,1 (1.173 THz) J = 85,3 - 76,2 (1.191 THz) J = 63,3 - 54,2 (1.542 THz) Self-broad: amplitude modulation Self-broad: amplitude modulation N2- & O2-broad frequency modulation N2- & O2-broad frequency modulation Cazzoli et al. JQSRT 2008 Cazzoli et al. JQSRT submitted *Cazzoli et al. JQSRT in preparation

  23. H2O: THz pure rotational lines investigated J = 31,2 - 30,3* (1.097 THz) J = 11,1 - 00,0 (1.113 THz) J = 72,5 - 81,8 (1.147 THz) J = 31,2 - 22,1* (1.153 THz) J = 63,4 - 54,1* (1.158 THz) J = 32,1 - 31,2* (1.163 THz) J = 85,4 - 76,1 (1.168 THz) J = 74,4 - 65,1 (1.173 THz) J = 85,3 - 76,2 (1.191 THz) J = 63,3 - 54,2 (1.542 THz) What was available for these lines? • - experimental values for 11,1 - 00,0 (N2& O2 ) • calculated and/or extrapolated data for others • - experimental values for 11,1 - 00,0 (N2& O2 ) • calculated and/or extrapolated data for others

  24. 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: previous exp data 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: previous exp data

  25. J = 11,1 – 00,0 transition of H2O T = 297 K Cazzoli et al. JQSRT 2008

  26. J = 11,1 – 00,0 transition of H2O T = 297 K Cazzoli et al. JQSRT 2008

  27. J = 11,1 – 00,0 transition of H2O T = 297 K Cazzoli et al. JQSRT 2008

  28. Self N2 O2 Air 297 K Exp Theo Exp Theo Exp Theo Exp Theo This work 19.72(46) 19.8 4.38(15) 4.2 2.40(12) 2.5 3.96(13) 3.8 Gasster et al. 3.67(10) 2.99(37) 3.53(8) HITRAN 4.74 3.53(8) J = 11,1 – 00,0 transition of H2O Improvements wrt old measurements

  29. 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: HITRAN self broad 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: HITRAN self broad

  30. Cazzoli et al. JQSRT submitted

  31. Cazzoli et al. JQSRT submitted

  32. Cazzoli et al. JQSRT submitted

  33. Cazzoli et al. JQSRT in preparation

  34. Cazzoli et al. JQSRT in preparation

  35. SELF-broadening Exp Theo This work J = 31,2 - 30,3 21.98(22) 21.54 HITRAN 18.40 This work J = 11,1 - 00,0 19.72(46) 19.8 HITRAN 4.74 This work J = 72,5 - 81,8 17.96(34) 17.93 HITRAN 12.93 This work J = 31,2 - 22,1 19.57(18) 21.22 HITRAN 18.33 This work J = 63,4 - 54,1 14.97(8) 16.27 HITRAN 16.94 This work J = 32,1 - 31,2 19.23(11) 19.80 HITRAN 18.40 This work J = 85,4 - 76,1 11.12(26) 11.33 HITRAN 15.16 This work J = 74,4 - 65,1 11.98(27) 13.03 HITRAN 16.69 This work J = 85,3 - 76,2 11.66(8) 11.88 HITRAN 15.16 This work J = 63,3 - 54,2  17.56 HITRAN 16.94 What’s the problem?

  36. COMPARISON: semiclassical calc. (SC) vs HITRAN (assumption*) values *dependence of the broadening parameter on J”

  37. COMPARISON: semiclassical calculations (SC) vs HITRAN (exp*) values *IR lines: 600-1000 cm-1 (R. A. Toth)

  38. COMPARISON: semiclassical calculations (SC) vs EXP* values *Markov 1994, Cazzoli et al. 2007, Cazzoli et al. 2008

  39. HITRAN ref. # lines Mean %error #lines with %err > 25% 3 98 8.3 10 13 6 43.3 4 15 15 37.3 8 23 1 3.7 0 30 3 6.8 0 Ref. 51: Averaged values as a function of J” 31 2 39.6 2 36 1 24.7 0 50 43 14.7 7 51 1333 37.5 595 52 1 76.6 1 53 3 24.1 1 Suggestion: Make use of calculated values when no reliable experimental data are available

  40. 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: N2, O2 & air broad 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: N2, O2 & air broad

  41. Cazzoli et al. JQSRT submitted

  42. Cazzoli et al. JQSRT submitted

  43. Exp Theo AIR-broadening This work J = 31,2 - 30,3 3.970(82) 4.00 HITRAN 4.13 This work J = 11,1 - 00,0 3.96(13) 3.8 HITRAN 3.53(8) This work J = 72,5 - 81,8 3.508(20) 3.13 HITRAN 3.24 This work J = 31,2 - 22,1 3.935(75) 3.77 HITRAN 3.65 This work J = 63,4 - 54,1 2.911(60) 2.80 HITRAN 2.99 This work J = 32,1 - 31,2 3.857(57) 3.77 HITRAN 3.93 This work J = 85,4 - 76,1 2.287(66) 2.07 HITRAN 2.18 This work J = 74,4 - 65,1 2.765(34) 2.42 HITRAN 2.59 This work J = 85,3 - 76,2 2.462(24) 2.18 HITRAN 2.27 This work J = 63,3 - 54,2 3.805(72) 3.28 HITRAN 3.32 Good agreement!

  44. 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: shift & SD param 3) Experiment & Theory: Results - H2O: which lines - theo & exp results: shift & SD param

  45. Cazzoli et al. JQSRT 2008

  46. Cazzoli et al. JQSRT submitted

  47. Cazzoli et al. JQSRT submitted

  48. Cazzoli et al. JQSRT in preparation

  49. Conclusions  10 pure rotational THz water lines have been experimentally and theoretically investigated • Rather accurate experimental results have been obtained • Good agreement between experiment and SC calculations • Update for HITRAN self broadening parameters is suggested

  50. Thank you for your attention!

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