1. Long Range Proton-Migration in VUV Photoionization of Acetone Clusters Ken-ichi Hanaue, Yoshiyuki Matsuda, Ayako Yamada, Keisuke Ohta, Naohiko Mikami, and Asuka Fujii 65th International Symposium on Molecular Spectroscopy June 24, 2010 Ohio State University Department of Chemistry, Graduate School of Science, Tohoku University, Japan

2. Cluster cations of protic molecules IR spectroscopy based on VUV photoionization detection has been applied to cluster cations of protic molecules. JCP 131, 184304 (2009) PCCP 11, 1279 (2009). (NH 3 ) 2 + (CH 3 OH) 2 + (CH 3 COOH) 2 + JCP 129, 094306 (2008). VUV photoionization of protic molecular dimers intracluster H + - transfer between NH and OH Can a proton of CH (alkyl group) be transferred? Roles of solvents in VUV photoionization of solvated clusters?

3. This study Understanding of VUV one-photon ionization dynamics of acetone-H 2 O ○ IR spectroscopy based on VUV photoionization detection of neutral and cationic clusters. ○ Reaction route search with the GRRM (Global Reaction Route Mapping) method ? VUV photoionization acetone-H 2 O acetone: aprotic molecule neutralcation

4. Experiment and calculation IR spectroscopy of neutral clustersIR spectroscopy of cluster cations ion signal IR VUV S0S0 IE dissociation tt V’ IR V’ S0S0 IE dissociation ion signal tt VUV By changing the relative delaytime between of the IR and VUVpulses, IR spectroscopy of both neutral (precursor) and cationic (product) clusters in the VUV photoionization can be carried out. IR spectroscopy based on VUV (118 nm) photoionization detection Exp eriment Calculation GRRM (Global Reaction Route Mapping) method (Maeda & Ohno, 2004) search of reaction routes following photoionization

5. 2600 2800 3000 3200 3400 3600 3800 IR spectra of neutral acetone and acetone-Ar cluster cation 2800 3000 3200 3400 3600 Wavenumber / cm -1 acetone acetone + -Ar Scaled by 0.931 MP2/6-31++G** Scaled by 0.931 IR-VUV-PIS IR VUV IE S0S0 V’ ion signal VUV @ 118 nm VUV @ 128 nm neutral cation OH keto 16.2 kcal/mol enol 0 kcal/mol

6. neutral cation acetone-H 2 O (acetone-H 2 O) + 2800 3000 3200 3400 3600 Wavenumber / cm -1 2600 2800 3000 3200 3400 3600 3800 Wavenumber / cm -1 H-bonded free OH low IR power CH OH 3 1 H-bonded OH IR spectra of acetone-H 2 O and (acetone-H 2 O) + MP2/6-31++G** scaled by 0.94 scaled by 0.948MP2/6-31++G** cyclic-type the alkyl proton migrates ! 118 nm photo -ionization detection 118 nm photoionization

7. two possible mechanisms photo- ionization proton-relay catch & release Proton migration mechanism enol form with the proton migration cation keto form VUV photoionzation proton-migration induced by photoionization neutral

8. neutral acetone-D 2 O acetone-D 2 O cation 2600 2800 3000 3200 3400 3600 3800 Wavenumber / cm -1 2800 3000 3200 3400 3600 3800 Wavenumber / cm -1 free OD CH H-bonded OH no free OH proton-migration catch & release IR spectra of neutral and cationic acetone-D 2 O clusters

9. catch & release Proton-migration induced by photoionization Proton-migration in ionization process Calculated isomerization path in photoionization with the GRRM method PBE1PBE/6-311+G(2d,2p) catalytic action of the water molecule enol I enol II

10. Intracluster proton-transfer from CH occurs upon the photoionization. IR spectroscopy based on VUV photoionization detection and reaction route search with the GRRM method were carried out to study VUV one-photon ionization dynamics of the acetone-water cluster. enol type cation neutral proton-migration Summary catch & release VUV The water molecule acts as the “catch & release” catalyst in the proton- migration. acetone-water ionization

11. apparatus fragment ion Ion Intensity IR frequency parent ion Ion Intensity spectroscopy of neutral and cations spectroscopy of cations Setup I TOF & DFG Setup II Tandem Q-mass & IR-OPO dip spectrum enhancement spectrum IR frequency

12. Mass spectrum of photoionization @118 nm 12 13 14 15 TOF /  s Mass spectrum of acetone-H 2 O @118 nm (acetone-H 2 O) + (acetone) + no higher clusters

13. 2600 2800 3000 3200 3400 3600 Wavenumber / cm -1 Scaled by 0.948MP2/6-31++G** 1 3 free OH CH x10 H-bonded OH CH H-bonded OH CH 1 3 1 3 1 3 H-bonded OH absorption (a) (b) (c) (d) (e) (a) H + -migrated 0 kcal/mol (b) H + -migrated II 0.7 kcal/mol (c) Charge-shared I 26.4 kcal/mol (d) Charge-shared II 29.2 kcal/mol (e) H-transferred 33.2 kcal/mol IR spectrum of acetone-water cluster cation IRPDS-VUV-PI @118 nm