Free O  H Anharmonic Stretching Motions in H  (CH 3 OH) 1  3 with or without Attached Argon 2014/06/19, 10:56-11:11 AM Hsiao-Han Chuang 1 Jer-Lai Kuo 2, Kaito Takahashi 2, Asuka Fujii 3 International Symposium on Molecular Spectroscopy, 69 th meeting June 15-20, 2014, Champaign-Urbana, Illinois, USA RC09 1. Department of Chemistry, National Taiwan University, Taipei, Taiwan (R.O.C) Nano Science and Technology Program, Taiwan International Graduate Program Institute of Physics, Academia Sinica, Taipei, Taiwan (R.O.C) 2. Institute of Atomic and Molecular Science, Academia Sinica, Taipei, Taiwan (R.O.C) 3. Department of Chemistry, Tohoku University, Sendai, Japan 1

Condensed phases Gálvez et al, JPC A, 2009, 113, 3321 Clusters Kobayashi et al, PCCP, 2013, 15, 9523 Hamashima et al, JPC A, 2013, 117, Clusters: the Bridge from Molecules to Bulk Isolated molecules

Ionic Clusters with Strong Binding Energy J. Chen et al, J Org. Chem. 2005, 3263,

Free O-H stretching of neutral methanol 3681 cm -1 4 Binding energy 2.67 kcal/mol Pre-Dissociation Spectra of Protonated Methanol Cluster B3LYP/6-31+G(d,p)

[H  O]  [O  H]  Ar---[H  O]  [O  H]  ---Ar AS S Ar  AS Ar  S E Using Local Mode Concept to Construct a Simple Messenger Effect Picture 5

Anharmonicity Coordinate Harmonic Approximation Anharmonic Potential Energy Curve 1. Dimensionality 2.Coordinate 3.Higher order term in Taylor expansion 6 Energy Real system Symmetric stretching Asymmetric stretching NMA LMA Variation theoryPerturbation theory PT2/Harm

Why the Correction of 1D Normal Mode Analysis Even Worse in Some Systems? 1.Dimensionality 2.Coordinate 3.Higher order term in Taylor expansion ν Harm. (S): 3649 ν Harm. (AS): D  NMA ν 2D-NMA (S): 3487 ν 2D-NMA (AS): 3574 Unit : cm  1 Harm. Approx. 1D  NMA ν 1D-NMA (S): 3566 ν 1D-NMA (AS): 3839 B3LYP/6-31+G(d,p) Blue: Harm. Approx. Red: 1D-NMA 7

Using Different Coordinate 1.Dimensionality 2.Coordinate 3.Higher order term in Taylor expansion Unit : cm  1 1D-NMA 1D-LMA Benchmark Exc:MP2, BLYP, B3LYP, ωB97, ωB97X, ωB97XD, BH&H, BH&HLYP Basis set: 6-31+G(d,p) ω 1D-LMA is higher than ω 1D-NMA Comparison B3LYP/6-31+G(d,p) 8

1.Dimensionality 2.Coordinate 3.Higher order term in Taylor expansion 1D-NMA k 2,3,4…∞ Variation Different Hamiltonian and Vibrational Calculation in Normal Mode Coordinate Benchmark Exc:MP2, BLYP, B3LYP, ωB97, ωB97X, ωB97XD, BH&H, BH&HLYP Basis set: 6-31+G(d,p) Unit : cm  1 9 Almost the same V. Barone J Chem. Phys. 2005, 122, coeff.(PT2/Harm) k 2,3,4 Variation 1D-PT2/Harm k 2,3,4  26 Perturbation Using different vibrational calculation VPT2 k 2,3,4  28 Perturbation k 2,3,4 Variation coeff.(1D-NMA) 53 Neglecting the higher order term

Computational Details Vibration calculation – Normal mode analysis (NMA) Using variational method on normal mode coordinate Level of theory – E xc : B3LYP – Basis set: 6-31+G(d,p) 10 H  (MeOH) n Ar m n=1~3 m=0~2

Bare Ionic Protonated Methanol Cluster Dimensionality (S) (AS) H  (MeOH) n Ar m n=1~3 m=0 Harm. 2D-NMA; B3LYP/6-31+G(d,p) (S) (AS) (LM)

How Argon Perturbed the O-H Stretching Gray Background: Experimental spectra Vibrational Calculation : Harm. 2D-NMA; B3LYP/6-31+G(d,p) H  (MeOH) n Ar m n=1~3 m=0~2 12 (S) (Ar) (AS) (Fr) (Ar-AS) (Ar-S)

E Using Local Mode Concept to Construct a Simple Messenger Effect Picture 13

[O  H]  Ar---[H  O]  E Using Local Mode Concept to Construct a Simple Messenger Effect Picture 14 AS S Ar  AS Ar  S Value of m Blue shift Red shift n=1, m=1

How the Argon Effect Picture Change while Cluster Size Increasing? 15 [  H]  Ar---[H  ]  AS S Ar  AS Ar  S [  H]  Ar---[H  ]  AS S Ar  AS Ar  S 2D-NMA; B3LYP/6-31+G(d,p)

This Messenger Effect Picture also Works on Experimental spectra 16

[O  H]  Ar---[H  ]  AS S Ar  S Ar  S Replace Argon with Weaker-Binding-Energy Noble Gas: Neon 17 2D-NMA; B3LYP/6-31+G(d,p)

Conclusion 1.Increasing the cluster size, the free O  H stretching is blue-shift and converged to the neutral case By using the local mode concept, we construct a simple messenger effect picture. The result shows that attached argon not only perturbs the O  H stretching which it binds on, but also affects their neighbor. 2.Free O-H stretching in methanol cluster is a relatively cleaner system that we can use it to benchmark several vibrational calculation.

19

Backup 1.The Role of Messenger 20

The Role of Messenger 21 Mass-selected beam Low density cluster First mass analyzer Second mass analyzer M. Okumura et al. J. Phys. Chem. 1990, 94, J.M. Price et al. J. Phys. Chem. 1991, 95, Daughter ions