1

Free O-H Anharmonic Stretching Motions in H+(CH3OH)1-3 with or

without Attached Argon2014/06/19, 10:56-11:11 AM

Hsiao-Han Chuang1

Jer-Lai Kuo2, Kaito Takahashi2, Asuka Fujii3

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

2

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, 101

Clusters: the Bridge from Molecules to Bulk

Isolated molecules

3

Ionic Clusters with Strong Binding Energy

J. Chen et al, J Org. Chem. 2005, 3263, 4611.

4380036002600 2800 3000 3200 3400

Free O-H stretching of neutral methanol

3681 cm-1

Binding energy2.67 kcal/mol

2.56

1.06

1.03

0.52

0.51

Pre-Dissociation Spectra of Protonated

Methanol Cluster

B3LYP/6-31+G(d,p)

5

[H-O]+ [O-H]+

Ar---[H-O]+ [O-H]+---Ar

AS

SAr-AS

Ar-S

E

Using Local Mode Concept to Construct a Simple Messenger Effect Picture

6

Anharmonicity

Coordinate

Harmonic Approximation

Anharmonic Potential Energy Curve

1. Dimensionality

2. Coordinate3. Higher order term in Taylor expansion

Energy

Real system

Symmetric stretching Asymmetric stretchingNMA LMA

Variation theory

Perturbation theory

PT2/Harm

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Why the Correction of 1D Normal Mode Analysis Even Worse in Some Systems?

1. Dimensionality2. Coordinate3. Higher order term in Taylor expansion

νHarm.(S): 3649

νHarm.(AS): 3743

2D-NMA

ν2D-NMA(S): 3487

ν2D-NMA(AS): 3574

Unit : cm-1Harm. Approx. 1D-NMA

ν1D-NMA(S): 3566

ν1D-NMA(AS): 3839

B3LYP/6-31+G(d,p)Blue: Harm. Approx.Red: 1D-NMA

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Using Different Coordinate

1. Dimensionality2. Coordinate3. Higher order term in Taylor expansion

Unit : cm-11D-NMA

1D-LMA

BenchmarkExc:MP2, BLYP, B3LYP, ωB97, ωB97X, ωB97XD, BH&H, BH&HLYPBasis set: 6-31+G(d,p)

ω1D-LMA is higher than ω1D-NMA

Comparison

B3LYP/6-31+G(d,p)

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1. Dimensionality2. Coordinate3. Higher order term in Taylor expansion

1D-NMAk2,3,4…∞

Variation

Different Hamiltonian and Vibrational Calculation in Normal Mode Coordinate

BenchmarkExc:MP2, BLYP, B3LYP, ωB97, ωB97X, ωB97XD, BH&H, BH&HLYPBasis set: 6-31+G(d,p)

Unit : cm-1

Almost the same

V. Barone J Chem. Phys. 2005, 122, 014108

coeff.(PT2/Harm)k2,3,4Variation

1D-PT2/Harmk2,3,4

-26

Perturbation

Using different vibrational calculation

VPT2k2,3,4

-28

Perturbation

k2,3,4

Variation

coeff.(1D-NMA)

53

Neglecting the higher order term

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Computational Details

• Vibration calculation– Normal mode analysis (NMA)• Using variational method on normal mode coordinate

• Level of theory– Exc: B3LYP

– Basis set: 6-31+G(d,p) H+(MeOH)nArm

n=1~3m=0~2

Bare Ionic Protonated Methanol Cluster

Dimensionality

(S)

(AS)

H+(MeOH)nArm

n=1~3m=0

Harm. 2D-NMA; B3LYP/6-31+G(d,p)

(S)

(S)

(AS)

(AS)

(LM)

162

165

165

164

163

169

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How Argon Perturbed the O-H Stretching

Gray Background: Experimental spectraVibrational Calculation : Harm. 2D-NMA; B3LYP/6-31+G(d,p)

H+(MeOH)nArm

n=1~3m=0~2

(S)

(Ar)

(AS)

(Fr)

(Ar-AS)(Ar-S)

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E

Using Local Mode Concept to Construct a Simple Messenger Effect Picture

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[O-H]+

Ar---[H-O]+

E

Using Local Mode Concept to Construct a Simple Messenger Effect Picture

AS

SAr-AS

Ar-S

Value of m0 1 2

12( 𝐴𝑆+𝑆)

12( 𝐴𝑟−𝐴𝑆+𝐴𝑟 −𝑆)

Blue shift

Red shift

n=1, m=1

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How the Argon Effect Picture Change while Cluster Size Increasing?

[ -O H]+

Ar---[H-O]+

AS

S

Ar-AS

Ar-S

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12

4

44

2

22[ -O H]+

Ar---[H-O]+

AS

S

Ar-AS

Ar-S

2D-NMA; B3LYP/6-31+G(d,p)

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This Messenger Effect Picture also Works on Experimental spectra

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0 1 23250

3300

3350

3400

3450

3500

3550

3600

Ne

n=1

m

Fun

dam

enta

l (cm

-1)

0 1 23100

3150

3200

3250

3300

3350

3400

3450

3500

3550

3600

Ar

n=1

m

Fun

dam

enta

l (cm

-1)

[O-H]+

Ar---[H-O]+

AS

S

Ar-S

Ar-AS

12( 𝐴𝑆+𝑆)

12( 𝐴𝑟−𝐴𝑆+𝐴𝑟 −𝑆)

1817

22

44

Replace Argon with Weaker-Binding-Energy Noble Gas: Neon

2D-NMA; B3LYP/6-31+G(d,p)

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Conclusion

1. Increasing the cluster size, the free O-H stretching is blue-shift

and converged to the neutral case.

3. 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.

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Backup

1. The Role of Messenger

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The Role of Messenger

Mass-selected beam

Low density cluster

First mass analyzer

Second mass analyzer

M. Okumura et al. J. Phys. Chem. 1990, 94, 3416.J.M. Price et al. J. Phys. Chem. 1991, 95, 2182.

Daughter ions