Ab initio predictions for HO2+: Theoretical Guidance for

Ab initio predictions for HO2+: Theoretical Guidance for

Ab initio predictions for HO2+: Theoretical Guidance for an Astronomical Detectability Study David E. Woon, Susanna L. Widicus Weaver, Branko Ruscic, and Benjamin J. McCall FD0 9 HO2+: Another Approach to the O2 Problem? Molecular oxygen (O2) is a difficult species to observe. The only observation to date the Odin study of Oph A [Larsson A&A 2007, 466, 999] found a limited abundance, just 5 x 10-8 relative to [H2]. This is much less than predicted by models, ~5-10 x 10-6 [Goldsmith, ApJ 2000, 539, 123]. It has been recognized for at least three decades [Herbst, ApJ 1977, 215, 503] that protonated forms of species that are diffi-cult to detect can be useful tracers of the parent no , A good example is N2H+, which molecules. microwa was observed well before N2 ve inactive

was finally detected. [Turner, ApJ 1974, 193, L83; Green, ApJ 1974, 193, L89; Knauth, Nature 2004, 429, 636]. large , good spectrum HO2+: Another Approach to the O2 Problem? While O2 does have observable weak dipoleallowed magnetic transitions, atmospheric spectral interference seriously impedes groundbased observations. Can HO2+ be used as a tracer 3 for O2? A 1.934 D 1.518 D MRCI/aug-ccpV5Z No rotational spectrum has yet been reported for HO2+, which currently precludes astronomical searches. A wide range of data is available for HO2 and can be used to benchmark theoretical calculations for HO2+. The best prior theory study is the work of Robbe et al. [Chem Phys 2000, 252, 9]. HO2+: Ab initio Predictions

Quantum chemical calculations were performed to evaluate the most likely pathway to the formation of HO2+ and to provide guidance for the laboratory study of its rotational spectrum. reaction dipole moment energetics rotational zero-field splitting constants tensor anharmonic spin-rotation frequencies constants Treatment: MRCI and RCCSD(T) calculations with basis sets as large as aug-cc-pV5Z. Programs used included: MOLPRO optimizations and potential energy surfaces SURFIT fitting and analysis of surfaces Formation of HO2+ from O2 and H3+ H3 + + O2 H2 + HO2+ Most likely formation pathway: H3+ + O2 H2 + HO2+ H 3 O2 + (1)

The reaction energy for this can be derived from the proton affinities of H2 and O2: H2 + H+ H3+ (2) PA(H2) = 0 H r O +(2)H+ HO + (3) PA(O ) = 2 2 rH0(3) The reaction enthalpy of (1) is: rH(1) = PA(H2) PA(O2) 2 Parallel expressions exist for Gs: gas phase basicities replace PAs. Formation of HO2+ from O2 and H3+ NIST WebBook values: PA(H2 ) = 100.93 kcal/mol

PA(O2) = 100.62 kcal/mol endothermic by 0.31 kcal/mol? However, Ruscic et al. [JPCA 2006, 110, 6592] recommended: exothermic by 0.05 PA(O2) = 100.98 0.14 kcal/ kcal/mol? mol ? which led to the collaboration with Branko Ruscic of ANL. Active Thermochemical Tables (ATcT) analysis of available data (will be described in FD10) Calculations for H3+ + O2 HO2+ + H2 Ee valence complete basis set (CBS) limit: +222.1 cm-1 Ee core-valence contribution +28.3 harmonic vibrational ZPE correction -199.5

anharmonic vibrational ZPE correction rotational ZPE correction +76.4 -63.0 H3+ [Lindsay, JMS 2001, 210, 60]: 64.121 cm-1 O2 [Cosby, JCP 1992, 97, 6108]: E01.0857 NET, Theory cm-1 1 rE00 from ATcT analysis cm-1 - +64.3 cm+509 VERY slightly endotherm ic Equilbrium Structure HO2 Treatment rOO () rOH () () RCCSD(T) Valence CBS 1.3270

0.9709 104.458 +CVDZ 1.3247 0.9701 104.549 Robbe et al. 1.337 0.968 103.90 HO2+ Treatment rOO () rOH () () RCCSD(T) Valence CBS 1.2295 1.0110 112.529

+CVDZ 1.2272 1.0102 112.743 Robbe et al. 1.237 1.007 111.8 Anharmonic Properties Potential energy surfaces were fit with SURFIT to 84 energy calculations distributed around the equilibrium structure for a given level of theory and basis set. The potential function include 69 terms consisting of the full quintic potential and selected sextic terms. All RMS -1 Perturbation wascm used fitting errors theory were <0.8 . for anharmonic shifts:

i = i + ( xii, xij ) - anharmonicities B0 = Be iB - rotation-vibration interaction constants (similar for A and C) Rotational Constants HO2 rotational constant (error) (GHz) A0 B0 C0 Experimenta This work 610.2 73 615.9 33.51 8 33.60 31.66 8 31.64 Robbe et al.

97 (+5.72 4) 612.2 4 (+0.08 6) 33.24 3 (0.025) 31.44 a Chance, JMS 1997, 183,05 518. 7 8 HO2+ rotational constant (GHz) A0 B0 C0 This work 659.3

01 38.34 4 35.88 5 Vibrational Frequencies HO2 frequency (error) (cm-1) 1 2 3 Experimenta 3436 1392 1098 This work 3457 1406 1128

(+21) (+14) (+30) 3449 1396 1106 Robbe et al. Yamada, JCP 1983, 78, 4379; Burkholder, JMS 1992, 151, 493. a HO2+ 1 This work frequency (cm-1) 2 3 3028 1440 1068

Dipole Moment Components HO2 dipole moment (error) (D) a b Experimenta 1.412 1.541 This work 1.405 1.572 (0.007) a Saito, JMS 1980, 80, 34. (+0.03 1) HO2+ dipole moment (D) a b This work

1.518 1.934 Zero-Field Splitting Magnetic interactions between the unpaired electrons in triplet states give rise to line splitting even in the absence of an applied field. ORCA [Neese et al., Universitt Bonn] was used to compute the spin-spin (SS) and spin-orbit coupling (SOC) contributions to the D and E tensors. Molecular oxygen O2 (3g-) was used for benchmarking. See Ganyushin & Neese [JCP 2006, 125, 024103] and Neese [JCP 2007, 127, 164112] for more extensive comparisons. DSS (ESS) was computed at the CASSCF/AVQZ level, while DSOC (ESOC) was computed at the MRCI/VQZ level and involved summing over four states each of singlet and triplet symmetry. Zero-Field Splitting O2 HO2+ this work this work DSS

1.555 1.810 DSOC 2.220 5.060 3.775 6.870 ZFS (cm1 ) D ESS EXPT a 3.9 6 0.013 ESOC

0.020 E 0.033 Tinkham, Phys Rev 1955, 97, 937. a Spin-Rotation Coupling Constants = 4B <0|L|n> ( E0 En ) n0 ; = 151 cm- 1 [Barnes, JMS 1978, 72, 86] Angular momentum matrix elements: CASSCF Energies: MRCI

Basis set convergence was tested with AVDZ and AVTZ sets HO2: sum over 4 states of 2A and 2A symmetry HO2+: sum over 4 or 6 states of 3A and 3A symmetry Spin-Rotation Coupling Constants HO2 EXPT a aa bb cc a 49572 422.9 8.748 HO2+ this work this work 4 sts 6 sts 4673 -432 0 -159

1094 -467 1182 -481 -429 -476 Fink, JMS 1997, 185, 304. Part II: Astronomical Detectability of HO2+ Hang around for Susannas talk... Acknowledgments DEW: NASA Exobiology Program, grant NNX07AN33G. SLWW: UIUC Critical Research Initiative program. BR: Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences, US Department of Energy, contract number DEAC02-06CH11357. BJM: UIUC Critical Research Initiative program, NSF CAREER award Kirk A.(NSF Peterson (Washington State CHE-0449592). University)

Frank Neese (Universitt Bonn) Thom H. Dunning, Jr. (University of Illinois) Configuration Diagrams for HO2+ A, 1 A 3 + A 1 A 3

Recently Viewed Presentations

  • Southern Gothic - George Mason University

    Southern Gothic - George Mason University

    Southern Gothic in American Literature Laurie Miller Background Sub-genre of the Gothic style Popular in Europe in 1800s Frankenstein by Mary Shelley Dracula by Bram Stoker Unique to American literature relies on supernatural, ironic or unusual events to guide the...
  • Advertisement for Television

    Advertisement for Television

    1.Propp's Theory. Every narrative has a * Hero * Helper * Villain * Damsel-in-distress. 2. Todorov's Theory * Equilibrium * Disruption * Resolution. 1. narrative. What is a ANTI-REALIST narrative advert?
  • World History - AP Human Geography

    World History - AP Human Geography

    People Without BordersIn many parts of Africa, country borders do not affect daily life. People often come and go without passports. People within an ethnic group share a language and a culture. In Africa south of the Sahara, identifying with...
  • Angles of Elevation & Depression What are we

    Angles of Elevation & Depression What are we

    SWBAT solve problems involving angles of elevation and depression using SOHCAHTOA. Skills Check. Let's review the vocabulary! Don't worry about writing this down in your notes. ... PowerPoint Presentation Last modified by: Windows User ...
  • Public Forums - Connecticut

    Public Forums - Connecticut

  • Method Section Describing the procedure Created by Alice

    Method Section Describing the procedure Created by Alice

    Steps in this tutorial. 1) State the goals of this tutorial. 2) What is a method section. 3) What is in a method section. 4) What is the procedure part of a method section
  • Grundlagen von XML - HTWK Leipzig

    Grundlagen von XML - HTWK Leipzig

    Grundlagen von XML Geschichte Grundidee „generic coding" - Trennung Information/Form formal definierter Dokumenttyp verschachtelte Strukturen Hypertext Extensible Markup Language (XML): "Erweiterbares HTML" Zusammenwachsen von SGML and HTML: Stärke von SGML (Dokumentenbeschreibungs-sprache) plus Einfachheit von HTML HTML vs. XML HTML beschreibt...
  • How to structure Class Preparation Assignments that really

    How to structure Class Preparation Assignments that really

    Yamane, D., 2006, Course Preparation Assignments: A Strategy for Creating Discussion-based Courses, Teaching Sociology, Vol. 34, 2006. A full-scale, well written 12 page paper on What-Why-Hows of CPAs. Anonymous, Getting Students to Prepare for Class, Teaching and Learning Center, University...