1. N 2 -CO 2 Consequences for Global Warming? Daniel Frohman Wesleyan University TH01 June 22, 2010

2. Motivation for study N 2 is the most abundant atmospheric species ~ 78% CO 2 is of importance as a greenhouse gas Complexation is expected to influence CO 2 ’s role as a greenhouse gas Study of the N 2 -CO 2 suggested by Prof. Klemperer (Harvard) and built upon previous work in a Wesleyan senior thesis by Edwin Contreras ’00

3. mode of CO 2 Occurs at 667.5 cm -1 in free CO 2 (1) Corresponds to bending motions Earth’s thermal emission spectrum maximizes at the mode of CO 2 (1) Phys. Rev. 41 (1932) 291 P. Martin & E. Barker

4. Influence on of complexation Q-branch narrow relative to P & R branches CO 2 Q-branch (∆J=0) is saturated by rot. transitions Complexation may alter Q-branch rot. transition saturation  CO 2 absorption changes http://www.spectralcalc.com/calc/spectralcalc.php http://www.spectralcalc.com/calc/spectralcalc.php Spectral Calculator GATS, Inc. ParameterValue Species 12 C 16 O 2 Pressure1013.25 mbar Temperature298 K Concentration380 ppm Path length10 cm

5. N 2 -CO 2 ’s CO 2 bending (ab initio) Gaussian 09 MP2/aug-cc-pVTZ 656.33 cm-1659.94 cm-1 CO 2 (exptl.) = 667.5 cm -1 CO 2 (G09) = 658.98 cm -1

6. 14 N 2 CO 2 Spectrum 2 02 - 1 01 Ortho: I=0,2 Para: I=1  separate constants for each improves fit, suggests N 2 tunneling No odd K a transitions FTMW++

7. 5 05 -4 04 Zoom View

8. Isotopomer spectrum Only 14 N(I=1), not 15 N(I=1/2) causes quadrupole splitting Isotopomer spectra less complicated Obtained in natural abundance 14 N 15 NCO 2

9. Ab initio & Counterpoise Gaussian 09 MP2/aug-cc-pVTZ Counterpoise (CP) correction adjusts geometry from skewed to (C2v) T-shaped & R CN increases G09 frequency with APF-D/3Za1P  A 0, B 0, C 0 and much faster than MP2/aug-cc-pVTZ CP corrected BDE 0.93 kcal/mol, uncorrected BDE 1.18 kcal/mol Method/Basis SetA (MHz)(B+C)/2 (MHz) MP2/aug-cc-pVTZ11538.252 (A e )1917.791 (B e +C e )/2 APF-D/3Za1P11749.004 (A e )1890.305 (B e +C e )/2 APF-D/3Za1P11899.104 (A 0 )1861.330 (B 0 +C 0 )/2 Obs.11885.3 (IR) (1) 1903.370 (para) R CN = 3.15 Å (1) Dyke, Howard, Walsh, J.Mol.Struct. 189 (1988) p. 111

10. Observed Structure ParameterValue (para I=1) Θ a (N 2 )19.52° Θ a (CO 2 )87.7°, 92.3° 3.727 Å -4.471 MHz (1) Mol.Phys. 84 (1) (1995) 185-199 J. Hutson Kisiel, Z., PMIFST, in PROSPE-Programs for Rotational SPEctroscopy. http://info.ifpan.edu.pl/~kisiel/prospe.htm.http://info.ifpan.edu.pl/~kisiel/prospe.htm

11. Constants Kisiel, Z., PMIFST, in PROSPE-Programs for Rotational SPEctroscopy. http://info.ifpan.edu.pl/~kisiel/prospe.htm.http://info.ifpan.edu.pl/~kisiel/prospe.htm 14 N 2 CO 2 (ortho) 14 N 2 CO 2 (para) 14 N 15 NCO 2 15 N 14 NCO 2 A11885.3 11878.8911871.77 B2062.75 (7)2062.88 (7)2037.95 (9)1999.76 (12) C1744.01 (7)1743.86 (7)1725.90 (9)1698.71 (12) ∆2.262.302.292.22 A – (B+C)/29981.929981.939996.9610022.53 (B+C)/21903.3789 (4)1903.3699 (5)1881.9283 (6)1849.2347 (8) (B-C)/479.69 (3)79.76 (3)78.01 (4)75.26 (6) ∆ J (kHz)10.6 (3)10.0 (3)9.4 (3)9.6 (4) -4.4726 (8)-4.4710 (13)-4.5189 (16)-4.4585 (20) All values given in MHz unless otherwise specified A & A - (B+C)/2 were fixed with A from Dyke, Howard, Walsh, J.Mol.Struct. 189 (1988) p. 111 1 st N   2 nd N

12. Cross and Parallel Structures Represent transition states for N 2 tunneling Parallel structure N 2 rotates in the complex’s ab plane Cross structure N 2 rotates in the ac plane Barrier height of ~ 155 cm -1 (cross), 203 cm -1 (parallel), making the cross somewhat favored Gaussian 09

13. N 2 tunneling w.r.t. N, N interchange

14. Atmospheric [CO 2 ] Favorability of complex formation and [CO 2 ] vary with location in atmosphere Atmosphere is complicated system making K eq difficult to get Simplified model of temperature and pressure as a function of altitude Estimates suggest influence by N 2 CO 2 in CO 2 ’s overall role as a greenhouse gas likely negligible

15. Results Experimental and ab initio data indicate the N 2 -CO 2 complex is T-shaped Separate constants for ortho and para states indirectly suggest that N 2 tunneling occurs in a non-rigid N 2 -CO 2 complex similarly to that in N 2 OCS (1) 17.02 cm -1 30.41 cm -1 62.20 cm -1 76.30 cm -1 G09 APF-D/3Za1P Prof. George Petersson (1) JMolSpec 175 (1996) 85-98 J. Connelly, S. Duxon, S. Kennedy, B.Howard, J. Muenter

16. Acknowledgements Prof. Novick & Pringle Ross Firestone * Prof. Petersson * Wesleyan University ‘12

17. QUADRUPOLE SPLITTING Q is the nuclear quadrupole moment dyadic, E is the electric field gradient e is the charge of a proton, z n is in the nuclear spin direction, r is distance from center of nucleus to the charge (p137) q j is the molecular field gradient in the z direction, theta is angle between z axis in space and r (or I and J)pg 136, rho-jj is electron charge density for mj=J Kroto, H.W., Molecular Rotation Spectra. 1992, Mineola: Dover Publications, Inc. Townes, C.H. and A.L. Schawlow, Microwave Spectroscopy. 1955, New York: McGraw-Hill Book Company

18. Supersonic Velocity Derivation For monatomic ideal gas, like Ar Beijerinck, H. Physica, 1983 121C. P 425 Free Jet Sources, Miller, D. p. 17-18