Proton Stretch in H 4 O 2 + : Effect of Ar Jheng-Wei Li, Ying-Cheng Li, Kaito Takahashi and Jer-Lai Kuo Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan 70 th OSU Int. Symp. on Mol. Spectroscopy, University of Illinois Urbana-Champaign, USA, June/26/2015

Structural Evolution & Solvation of OH radical in (H 2 O) n +, n=5~8 En-Ping Lu, Piin-Ruey Pan, Ying-Cheng Li and Jer-Lai Kuo Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan Ming-Kang Tsai Dept of Chem., National Taiwan Normal University, Taipei, Taiwan 69 th OSU Int. Symp. on Mol. Spectroscopy, University of Illinois Urbana-Champaign, USA, June/19/2014

(H 2 O) n + vs. H + (H 2 O) n Mizuse, Kuo, Fujii, Chem. Sci., 2, 868 (2011)

IR Spectra of (H 2 O) n +, n=5~8 Vib. band ~ 3200 cm -1 is assigned to fully solvated OH. Direct evidence of solvated OH radical for n ≥ 7.

Protonated Water Dimer Cation: H 5 O 2 + IHB vibration = the doublet ~ 1000 cm -1 Full Dimensional Calculations on Joe Bowman’s

Water Dimer Cation: H 4 O 2 + IHB vibration = Multiple intense peaks ~2000 cm -1 For IHB, is Argon relevant ? Triplet rather than a single peak. H 4 O 2 + Ar 2 H 4 O 2 + Ar 1 Schaefer, H. F. et al. J. Phys. Chem. A 2009, 113, Johnson, M. A. et al. J. Phys. Chem. A 2009, 113, 4772

Outline Quick review on theoretical works Methodology Results Summary 7

Previous theoretical works - I E. Kamarchik, O. Kostko, Joel M. Bowman, M. Ahmed, and A. I. Krylov J. Phys. Chem. A, 113, 4772 (2009) PES is obtained by MP2/aug-cc-pVDZ (a) the outer bonds in H3O+ (b) the OO bond length, (c) the HOH angle (i.e., of the outer OH bonds in H3O+) (d) the dihedral angle corresponding to the orientation of the OH moiety

Previous theoretical works - II J. Chem. Phys., 132, (2010) PES is obtained with EOM-IP-CCSD/aug-cc-pVTZ IR spectra were done computed Presence of Ar is not included

Normal Mode Approx. (NMA) A simple DVR along normal mode direction (approx.) PES obtained from ab initio cal. (no approx.) Diagonalize the (no approx.) Intensities were calculated via Fermi Golden Rule (no approx.) We use harmonic grids on B3LYP/6-31+G(d,p)

Stretches(4D) Bends+Stretches(6D) Anharmonicity in H 3 O +..OH· Harm. 11

Effect of Ar on H + stretch (Structure)

OH radical Sym & Asym. Effect of Ar on H + stretch (Vib. Spectra) 6D (3 d(OH) + H + strech + 2 bends)

OH radical Sym & Asym. Effect of Ar on H + stretch (Vib. Spectra) 6D (3 d(OH) + H + strech + 2 bends)

Low-freq. vibrational modes 118cm cm cm cm cm cm -1

Possible origins of “Triplet” 114cm cm cm cm -1

What else? Location of Ar n=2 E = Eh ZPE = Eh E = Eh ZPE = Eh 2A 2B 2C E = Eh ZPE = Eh n=1 E = Eh ZPE = Eh E = Eh ZPE = Eh E = Eh ZPE = Eh 1A1C 1B 1A 1B

Summary Vibrational spectra of H 4 O 2 +..Ar 0,1&2 were computed. Strong coupling with two bending modes were found. A few low freq – vibrational modes are important too. Vibrational feature ~ 2000 cm -1 is sensitive to the position of Ar. Call for more exp. (Ne/He-tagged & 3 Ar-tagged) & full dimensional calculations on high quality PES.