High-Resolution Spectroscopic Studies of Reaction Intermediates relevant to Atmospheric Chemistry Yasuki Endo Department of Basic Science The University of Tokyo June/18/2014 ISMS 2014 Urbana

Main Research Interests High-resolution spectroscopy of short lived reactive species, and complexes FTMW spectroscopy : Observe pure rotational transitions LIF spectroscopy : Electronic transitions Short lived species in the gas phase esp. produced in a supersonic jet Carbon chain molecules Oxygen bearing species Radical complexes

Vis-UV Laser spectroscopic system YAG Laser pumped dye lasers with resolution up to 0.02 cm -1

FTMW spectrometer Balle-Flygare type FTMW spectrometer Observe pure rotational transitions in the 4 – 40 GHz region

Pulsed Discharge Nozzle Pulse Valve Pulsed electric discharge 1.0–2.0 kV, 0.2 msec Free radicals Discharge samples containing appropriate parent molecules in Ar or Ne (0.2 – 0.5 %) to produce target species Radical compexes

FTMW–mmW Double Resonance Method pump source PDN Sample MW cavity pulsed MW mm-wave as well as cm-wave sources can be used for the pump radiation. It is even possible to use optical or IR sources.

Oxygen Bearing Short lived Species Species with more than one oxygen atoms HOOH, HOO, FOO, O 3 (well known) X-OO, CH 3 OO, HOOOH, HOOO, … (oxygen chain species cf. carbon chain species) HOCO, H 2 CO 3, HCO 3, CH 2 OO, CH 3 CHOO CH 2 CHO, CH 2 CCHO Oxygen bearing radical complexes H 2 O–OH, Ar–HO 2, HO 2 –H 2 O CO–HOCO, H 2 O–HOCO CH 2 OO–H 2 O important in atmospheric chemistry

Studies of the HOCO Radical and the Carbonic Acid Important players in atmospheric chemistry CO, CO 2 H 2 O, OH, HO 2 Oxidation reaction of CO OH + CO → OH–CO (1) → HOCO → CO 2 + H Hydration of CO 2 CO 2 + H 2 O → CO 2 –H 2 O (2) → H 2 CO 3 (1) M. I. Lester, B. V. Pond, D. T. Anderson, L. B. Harding, A. F. Wagner, J. Chem. Phys. 113, 9889 (2000). (2) K. I. Peterson, W. Klemperer, J. Chem. Phys. 80, 3439 (1984).

Oxidation reaction of CO Relative energy (kcal/mol) –30 –20 – t-HOCO (TS4) t-HOCO (TS1) c-HOCO (TS1) OH–CO OH+CO H + CO 2 t-TS C 2v –M c-HOCO (TS2) C 2v –TS cis-HOCO trans-HOCO OH + CO → CO 2 + H reaction

trans-HOCO and cis-HOCO trans-HOCO Metastable state No gas phase spectra The most stable state Gas phase spectra known cis-HOCO 7.6 kcal/mol 1.8 kcal/mol

Spectra of cis- and trans-forms μ a = 1.3 Debye μ a = 2.5 Debye Iterations 1 01 –0 00 J=1.5–0.5, F=2–1 cis-HOCOtrans-HOCO 1 ： 4.5 Observed for the first time Discharge a mixture of CO and H 2 O in Ar

Molecular Structures of HOCO cis-HOCO trans-HOCO Data from HOCO and DOCO Red: assumed

Observation of CO–trans-HOCO 6 06 –5 05 finally 21 a-type transitions 2 b-type transitions has been observed

Determined Structure of CO–HOCO Å 176.6° exp. ab inito A (2) B (1) 1280 C (1) 1233 RCCSD(T) / aug-cc-pVTZ Carbon side is bonded Fairly short bond length

Possible Existence of the HOCO–H 2 O Complex cis-form of HOCO S. Aloisio, J. S. Francisco, J. Phys. Chem. A104, 404 (2000). Contribution of the existence of water on the oxidateion of CO

Cyclic Structure of the H 2 O–HO 2 Complex O1–H3: Å Fairly short cf Å (H 2 O) 2 K. Suma, Y. Sumiyoshi, and Y. Endo, Science 311, 1278 (2006)

Structures of the H 2 O–HOCO Complexes and their Relative Energies

Observed Spectra of H 2 O–trans-HOCO Two series with different hyperfine patterns

Molecular Constants of H 2 O–trans-HOCO A’A”ab initio a (B+C)/ (1) (1)2503  aa (2)  bb 2.43(1) 1.63(5)  cc (5) aFaF -3.12(6) -3.44(10) T aa 24.66(3) 24.87(14) T aa (H 2 O) 2.53(7) a RCCSD(T) / aug-cc-pVTZ

Determined Molecular Structures Å Å (ab initio) Very short hydrogen bond (c.a. 2.0 Å) Binding energy: 8.8 kcal/mol (ab initio) RCCSD(T) / aug-cc-pVTZ

Observation of the Carbonic Acid H 2 O + CO 2 H 2 O–CO 2 complex studied by FTMW spectroscopy H 2 CO 3 carbonic acid not detected in the gas phase

Past Theoretical Studies 3 isomers (1) cis-ciscis-transtrans-trans Stability (2) H 2 CO 3 + n H 2 O → CO 2 + (n + 1) H 2 O half-life, n = 0: 0.18 million years n = 1: 10 hours n = 2: 2 minutes Endothermic for the production of H 2 CO 3 half-life (log t /s) (1) B. Jönsson et al, Chem. Phys. Lett. 41, 317 (1976). (2) T. Loerting et al., Angew. Chem., Int. Ed. 39, 891 (2000).

Ab initio Calculations φ1φ1 φ2φ2 cis-ciscis-transtrans-trans MOLPRO CCSD(T)/cc-pVTZ Energy [kcal/mol] φ1φ1 φ2φ2

Molecular Structure of cis-trans H 2 CO ° 126.8° Å r(C=O) : Å (HCOOH) Å (H 2 CO) r(C–O) : Å (HCOOH) Å (CH 3 OH) ∠ (O=C–O) : 124.9°(HCOOH) Å Å Although this is a higher energy isomer, it has a large dipole moment and is rather easier to detect

Molecular Structure of cis-cis H 2 CO ° Å r(C=O) : Å (HCOOH) Å (H 2 CO) r(C–O) : Å (HCOOH) Å (CH 3 OH) ∠ (O=C–O) : 124.9°(HCOOH) Å It is the most stable isomer. Spectra were weaker since the dipole moment is smaller.

Isomers of H 2 CO φ1φ1 φ2φ2 cis-ciscis-transtrans-trans No spectrum was observed for the trans-trans isomer since the barrier to the cis-trans form is so low.

Detection of Bicarbonate Radical Slightly exothermic (RCCSD(T)/cc-pVTZ)

Observed Spectral Pattern Discharge H 2 O + CO 2 mixture, many paramagnetic lines

An Example of the Observed Line 1000 times accumulation 2 02 – 1 01 J = 2.5 – 1.5 F = 3 – 2 In general, signals were very weak

Determined Molecular Constants for HCO 3 exp.ab initio a FCO 2 b A (5) B (4) C (4)  aa –130.1(3)  bb –675.9(3)  cc –47.57(4) aFaF 9.96(5) T aa 5.60(3) T bb –0.68(3) a RCCSD(T)-F12a / aug-cc-pVTZ b L. Kolesnikova et al., JCP 128, (2008)

Detection of CH 2 OO Criegee Intermediate (CI): R 1 R 2 COO (carbonyl oxide) Intermediate in the ozonolysis process of alkene + O 3 Ozonolysis Process of Alkene: First proposed by Rudolf Criegee Justus Liebig Ann. Chem. 564, 9 (1949). Angew. Chem., Int. Ed. Engl. 14, 745 (1975).

Previous studies of CH 2 OO Gas-phase Spectra of CH 2 OO M. I. Lester group JACS 134, (2012). Y.P. Lee group Science 340, 174 (2013). No direct information for the structure… B-state: Repulsive

Observed Spectra of CH 2 OO CH 2 OO: CH 2 OO: FTMW spectrumFTMW-mmW DR spectrum 400-shots (CH 2 Br 2 + O 2 ) disch. now (CH 2 I 2 + O 2 ) disch. : very strong signals

Determined Molecular Structure of CH 2 OO Ab initioFit 1Fit 2 r OO / Å (1)1.345(3) r CO / Å (1)1.272(3) r CH (cis) / Å (15)1.094(1) r CH (trans) / Å (7)1.088(4) OOC / deg (2)118.02(3) OCH (cis) / deg (22)118.0(6) OCH (trans) / deg (13)114.9(fix)  fit / MHz long O-O bond zwitterion like structure Structure from CH 2 OO CD 2 OO CH 2 18 O 2 CD 2 18 O 2

More Papers for CH 2 OO FTMW, more isotopologues, refined structure M. C. McCarthy et al., J. Phys. Chem. Lett., 4, 4133 (2013) Sub-mm wave spectrum A. M. Daly et al., J. Mol. Spectrosc., 297, 16 (2014)

Detection of Methyl Derivatives Internal Rotation of the Methyl-tops Higher Barrier due to the interaction with O atom Lower Barrier 3.7 kcal/mol higher in energy

Rotational Transitions of syn-CH 3 CHOO UV absorption by J. M. Beames et al. JCP 138, (2013) red: FTMW blue: FTMW-mmw-DR (CH 3 CHI 2 + O 2 ) disch.

Observed Transitions of syn-CH 3 CHOO (a) FTMW spectrum (b) FTMW-mmw-DR spectrum Very small splittings for the internal rotation

Rotational Transitions of anti-CH 3 CHOO red: FTMW blue: FTMW-mmw-DR Signals are 1/3 – 1/4 times weaker than those of syn- CH 3 CHOO

Observed Transitions of anti-CH 3 CHOO Observed by FTMW spectroscopy Relatively Large A–E splittings EA

Determined Parameters for CH 3 CHOO

Water Complex of CH 2 OO Å Å Cyclic Structure (CCSD(T)/aug-cc-pVTZ) Double hydrogen bonds cf. H 2 O–HOO Relatively short OO...HO bond length Enhance hydrogen migration to produce the OH radical

Rotational Transitions of CH 2 OO–H 2 O (CH 2 I 2 + O 2 + H 2 O) disch. red: FTMW blue: FTMW-mmw-DR Tansitions of CH 2 OO–D 2 O were also observed (detection was confirmed)

Determined Parameters for the Water Complex

Determined Structure Å (1.872 Å) Å (2.114 Å) The hydrogen bond is shorter than usual Cyclic structure like HO 2 –H 2 O CH 2 OO: proton acceptor

Conclusions for the Studies of Criegees The simplest Criegee, CH 2 OO, was identified by FTMW spectroscopy, and structure has been determined. Nakajima and Endo, JCP 139, (2013) Both syn- and anti-forms of CH 3 CHOO were identified, where barriers for the internal rotations were determined. Nakajima and Endo, JCP 140, (2013) Criegee–Water complex, CH 2 OO–H 2 O, was identified by FTMW spectroscopy, and cyclic form was confirmed, which is expected to enhance the hydrogen migration producing the OH radical. Nakajima and Endo, JCP 140, (2014)

Other Studies Carbon chain species (FTMW and LIF) CCS, HCCN, CCCF, CCCCl, SiCCN, SiCCCN, SiCCH Vinoxy derivatives (FTMW and LIF) CH 2 =CHO, CH 2 =CHS, CHCH 3 =CHO, CH 2 =CCH 3 S, CH 2 =C=CHO Atom–diatom systems (FTMW) Rg–OH, Rg–SH, Rg–NO, Rg–CS

Acknowledgement Prof. M. Nakajima (U. Tokyo) Criegees Prof. Y. Sumiyoshi (Gumma Univ.) Dr. T. Mori (Horiba Co. Ltd.)H 2 CO 3, HCO 3 Dr. T. Oyama (Tokyo Science Univ.)HOCO and other graduate students Financial Support JSPS funds