Agns Perrin The n 5 2 n 9

Agnès Perrin The n 5 & 2 n 9 bands of the 15 N isotopic species of nitric acid (H 15 NO 3): Line positions & line intensities Agnés Perrin, J. -M. Flaud Laboratoire Interuniversitaire des Systémes Atmosphériques (LISA), CNRS, Université Paris XII, , France. Robert Mbiake, Centre de Physique Atomique et Moléculaire et Optique Quantique Université de Douala, BP 8580 Cameroun (CEPAMOQ), G. Brizzi, M. Carlotti, and M. Ridolfi Dipartimento di Chimica Fisica e inorganica, Bologna, Italy

Agnès Perrin The 11 µm region: used commonly for the retrieval of HNO 3 in the atmosphere (MIPAS, ACE…) => Previous studies involved: • the {n 5, 2 n 9} interacting bands of H 14 NO 3. • the n 5+n 9 -n 9 hot band of H 14 NO 3 Present study : {n 5, 2 n 9} bands of H 15 NO 3 Motivations • To improve the HNO 3 parameters at 11µm by providing parameters for H 15 NO 3 (a~0. 0036) • To test the quality of the model used for the line positions & intensities of the {n 5, 2 n 9} interacting bands of H 14 NO 3.

Agnès Perrin Experimental details • FTS spectrum recorded by Johns on the modified Bomem D 8. 002 spectrometer located at the Steacie Institute for Molecular Science at Otawa, National Research Council (Canada). R=0. 0014 cm-1 • P~0. 04 Torr, Path Length=28 x 30 cm, T=296 K, H 15 NO 3 isotopic sample We are grateful to Dr Johns for providing us with the H 15 NO 3 spectrum used for this study.

Agnès Perrin Analysis • We follow the (rather) regular series in n 5 & 2 n 9 using ground state # combination differences. Then we used the model which will be described in the next slides. • Only A-type transitions were observed for n 5 & 2 n 9 • 1453 & 691 energy levels were measured for 51 & 92 states. (5500 assigned lines, J<66) #Drouin, Miller, Fry, Petkie, Helminger, Medvedev J. Mol. Spectrosc. 235, (2006) 293

Agnès Perrin Theoretical model#, $ used for the {n 5, 2 n 9} bands of H 14 NO 3 • Very strong Fermi (& Coriolis) resonances 51 92 • . n 9 (OH torsion / NO 2) is a large amplitude mode • Torsional splittings# observed in the millimeter region for the rotational transitions in the 2 n 9 and (surprisingly enought) n 5 states. • Ratio of the torsional splittings (n 5/2 n 9)~ 0. 7 • Band intensity ratio (2 n 9/n 5)~0. 7 Both transferts (of intensity n 5 2 n 9) and (of torsion 2 n 9 n 5) have the same common origin in the strong Fermi (& Coriolis) resonances 51 9 2 #Petkie, Goyette, Helminger, Pickett, De Lucia J. Mol. Spect. 208 (2001) 121. $ Perrin, Orphal, Flaud, Klee, Mellau, Mäder, Walbrdt, Winnewisser J. Mol. Spect. 228 (2004) 375.

Hamiltonian model for H 14 NO 3 Agnès Perrin => The value F 0=8. 53018808(620) cm-1 was achieved from the torsional splitting (millimeter wave measurements) for the 2 n 9 & n 5 rotational transitions. #Petkie, Goyette, Helminger, Pickett, De Lucia J. Mol. Spect. 208 (2001) 121. $ Perrin, Orphal, Flaud, Klee, Mellau, Mäder, Walbrdt, Winnewisser J. Mol. Spect. 228 (2004) 375.

Agnès Perrin Hamiltonian model for H 15 NO 3 X X X No Tors 99: There was not yet millimeter wave measurements in n 5 or 2 are weaker for 15 N than for 14 N : non orthorhombic 15 NO 3 (see Thefor resonance 51 9 2 n H paper RG 03 by Petkie et al !!!) 9 terms in the v- diagonal blocks F 0 was maintained at the value F 0=8. 53018808(620) cm-1 which was achieved for H 14 NO 3 from millimeter wave #, $ measurements of 2 n 9 & n 5 rotational transitions. In this way, 82% of the 2000 levels were reproduced within 0. 0005 cm-1 #Petkie, $ Goyette, Helminger, Pickett, De Lucia J. Mol. Spectrosc. 208 (2001) 121 Perrin, Orphal, Flaud, Klee, Mellau, Mäder, Walbrdt, Winnewisser J. Mol. Spect. 228 (2004) 375.

Agnès Perrin Line intensities • There is (up to now) no line intensity data for H 15 NO 3. • We used the line intensity parameters (parameters involved in the expansion of the n 5 & 2 n 9 transition moment operators) achieved for H 14 NO 3. ( n 5 : 5 mz=0. 25 D; 2 n 9: 99 mz=-0. 007 D, 9 mx=0. 03 D) >> 99 m 9)=0. 322 H 15 NO 3 Int(n 55)=1. 41 ; Int(2 n m and 99 m H 14 NO 3 z x -1/(molecule. cm-2) Int(n 5)=1. 03 z; Int(2 n 9)=0. 750 (in 10 -17 cm Int(2 n 9)/Int(n 5)=0. 23 (H 15 NO 3 ) (0. 73 for H 14 NO 3)

Agnès Perrin

Agnès Perrin

Example of a resonance… Agnès Perrin

Agnès Perrin H 14 NO 3 and H 15 NO 3 simulated spectra. H 14 NO 3 Int(n 5/TOTAL)~0. 57 H 15 NO 3 For H 15 NO 3 : Int(n 5/TOTAL)~0. 8 Isotopic abundance only: a~0. 003 isotopic shift to the low frequency range Only a weak part of the n 5 band intensity is transfered to the 2 n 9 band

Agnès Perrin First observation of H 15 NO 3 in an atmospheric spectrum (MIPAS on the ENVISAT satellite) . n 5 Q branch of H 15 NO 3 The evidence of H 15 NO 3 in the atmosphere was achieved exploiting the features of the Residual and Error Correlation analysis.

Agnès Perrin Conclusion • The first analysis of the n 5 and 2 n 9 bands of H 15 NO 3 was performed • The theoretical model used for the analysis is directly issued from the one used for H 14 NO 3. • The ratio of the band intensity is Int(2 n 9/n 5)~0. 23 (significantly weaker than for H 14 NO 3). • Using these parameters, the first observation of the Q branch of the n 5 band of H 15 NO 3 was performed in MIPAS spectra • For additional informations on the millimeter wave structure of the n 5 and 2 n 9 bands of H 15 NO 3 : see paper RG 03 by Petkie et al.

Agnès Perrin H 14 NO 3 and H 15 NO 3 simulated spectra. => The intensity ratios of the n 5 and 2 n 9 bands are very different for the H 14 NO 3 and H 15 NO 3 isotopic species. 17. 33 cm-1 H 14 NO 3 Int(2 n 9/n 5)~0. 7 22. 35 cm-1 H 15 NO 3 Int(2 n 9/n 5)~0. 23

Agnès Perrin H 14 NO 3 and H 15 NO 3 simulated spectra. F 0=8. 53018808(620) cm-1 achieved for the H 14 NO 3 17. 33 cm-1 H 14 NO 3 Int(2 n 9/n 5)~0. 7 22. 35 cm-1 H 15 NO 3 Int(2 n 9/n 5)~0. 23

Agnès Perrin