Ohio State (Current and recent):Laura Dzugan Jason Ford Charlotte HinkleSamantha Horvath Meng Huang Zhou LinBernice Opoku-Agyeman Andrew Petit

Bethany Wellen

Experimental Collaborators:Michael Duncan Mark Johnson Carl LinebergerMarsha Lester Terry Miller Mitchio Okumura

DECODING THE EFFECTS OF LARGE AMPLITUDE

VIBRATIONAL MOTIONS IN SPECTRA

68th MSSJune 17, 2013

How are we taught to treat vibrational contributions to

spectra: Vibrations are based on harmonic oscillators Vibrational spectra:

selection rules (linear dipole/harmonic oscillator) are Δn = 1 Intensity of transition will depend on

SymmetryHow much the dipole moment is affected by vibration

(specifically dμ/dr)(in H-bonded systems this leads to intense transitions

associated with H-bonds) Electronic transitions (or electron photodetachment)

Frank-Condon spectra based on normal modes give a good first “guess” Intensity of transition will depend on

SymmetryHow much the structure of the molecule changes

Such calculations of vibrational spectra can be (relatively) easily performed using widely available programs

How well does this work?

E. Garand, M. Z. Kamrath, P. A. Jordan, A. B. Wolk, C. M. Leavitt, A. B. McCoy, S. J. Miller, M. A. Johnson, Science, 335 694 (2012).

2

21

nn q

I

Assumes:Harmonic

Experiment:

Often the harmonic picture provides a good qualitative starting point for

assigning spectra/identifying isomers that are present, etc…

… but sometimes it fails to provide an complete physical picture

cm-1

500 1000 1500 2000 2500 3000 3500 4000

calc

ula

ted s

ignal

(unscale

d h

arm

onic

)

0

1

2

3

4

5

6

1000 1500 2000 2500 3000 3500

Pre

disso

ciatio

n Yie

ld

Photon Energy, cm-1

Cl-(H2O)

Spectrum: Ben Elliot, Rob Roscioli and Mark Johnson, published in JCPA in 2010

As we look more closely, often there are many more peaks in the spectrum than can be accounted for by 3N-6 normal modes.

What are their presence and intensity telling us about the bonding in these

systems?

More on these systems in RG13 – Meng Huang

Harmonic spectrum of H3O2-

Photon energy

0 500 1000 1500 2000

Sig

na

l

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Experimentharmonic

For molecules with large amplitude motions harmonic treatments can fail

badly…

E. Diken and M. A. Johnson

Harmonic descriptions of photoelectron spectra (Franck

Condon approximation)

Simulation assume Franck-Condon approximation:

The intensity is determined by overlap of thermally populated states of the anion and neutral eigenstates

Electron Binding Energy (eV)

Pho

toel

ectr

on C

ount

s (

arb.

uni

ts)

2anionneut

mn vvI

K. M. Vogelhuber, S. W. Wren, A. B. McCoy, K. M. Ervin and W. C. Lineberger, JCP 134 184306 (2011)

For many systems, this approximation works very well, but …

X-

X + e-

Harmonic descriptions of photoelectron spectra (Franck

Condon approximation)

Large geometry change between anion and neutral coupled with large amplitude motion of neutral leads to break-down of harmonic FC treatment for CDCl2-

Electron Binding Energy (eV)

Pho

toel

ectr

on C

ount

s (a

rb.

units

)

K. M. Vogelhuber, S. W. Wren, A. B. McCoy, K. M. Ervin, and W. C. Lineberger, JCP 134 184306 (2011)

Some cautionary tales of “deficiencies” in harmonic picture

of molecular vibrations How should we think about anharmonic effects in molecular spectra? Electrical [non-linear terms in the dipole] Mechanical [higher order terms in the potential]

Are there simple models we can employ to anticipate and/or understand these effects?

Focus on five systems (with a few more along the way) Photoelectron spectrum of CHCl2-

Manifestations of anharmonicity in the formate.water complex

Investigating broad signatures of H-bonding Solvated H3O+ and insights gained about the origins of the

2100 cm-1 band in the spectrum of H2O(l)

H5+ - exciting into the dissociation coordinate

Harmonic descriptions of photoelectron spectra (Franck

Condon approximation)

Large geometry change between anion and neutral coupled with large amplitude motion of neutral leads to break-down of normal mode treatment for CDCl2-

Electron Binding Energy (eV)

Pho

toel

ectr

on C

ount

s (a

rb.

units

)

K. M. Vogelhuber, S. W. Wren, A. B. McCoy, K. M. Ervin, and W. C. Lineberger, JCP 134 184306 (2011)

What’s going on? Large geometry change Modes strongly coupled in

the neutral

Out-of-plane bend

HC

Cl +

HC

Cl’

xx

z

x

y

Anion Gnd State

FC active states of neutral

What’s going on? Large geometry change Modes strongly coupled

in the neutral

Anion Gnd State

FC active states of neutral

Lesson 1: large amplitude (out-of-plane) vibrations can challenge

harmonic treatments, but often they can be treated with simplified

reduced-dimensional approaches

Lesson 2: Coordinates matter

Some cautionary tales of “deficiencies” in harmonic picture

of molecular vibrations How should we think about anharmonic effects in molecular spectra? Electrical [non-linear terms in the dipole] Mechanical [higher order terms in the potential]

Are there simple models we can employ to anticipate and/or understand these effects?

Focus on five systems (with a few more along the way) Photoelectron spectrum of CHCl2-

Manifestations of anharmonicity in the formate.water complex

Investigating broad signatures of H-bonding Solvated H3O+ and insights gained about the origins of the

2100 cm-1 band in the spectrum of H2O(l)

H5+ - exciting into the dissociation coordinate

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Example of anharmonicity (formate.water complex)

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Helen Gerardi, Andrew DeBlase, X. Su, K. D. Jordan, ABM and M. A. Johnson (JPC-Lett, 2 2437 (2011).

VHarmonic/μLinear

nq2

nq1

0.0 0.2 0.4 0.6 0.8 1.0

Energy (arb. units)

Types of anharmonicity:q 2

q1q1

q 2

Pote

nti

al

(mech

an

ical)

Dip

ole

(ele

ctri

cal)

harmonic

V=k1 q12 + k2 q2

2 μ=d1 q1 + d2 q2

n2

n1

q 2

q1q1

q 2VHarmonic/μLinear

nq2

nq1

0.0 0.2 0.4 0.6 0.8 1.0

Energy (arb. units)

Effect of mechanical anharmonicity:

Pote

nti

al

(mech

an

ical)

Dip

ole

(ele

ctri

cal)

V=k1 q12 + k2 q2

2 μ=d1 q1 + d2 q2

q 2

q1q1

q 2

V=k1 q12 + k2 q2

2 + K12 q1q22

m=d1 q1 + d2 q2

VAnharmonic/μLinear

n2n1/2n2

0.0 0.2 0.4 0.6 0.8 1.0

Energy (arb. units)

anharmonic pot.

n2

n1

Calculated spectrum of H2CO(presented at MSS – Jun 1991)

harmonic

VPT2/VPT4based on a linear dipole moment

ABM and ELSibert, JCP, 95, 3488 (1991)

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Example of mechanical anharmonicity (intensity borrowing formate.water complex)

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Change in the potential

with vibration excitation

Fermi resonance(intensity borrowing)

Helen Gerardi, Andrew DeBlase, X. Su, K. D. Jordan, ABM and M. A. Johnson (JPC-Lett, 2 2437 (2011).

IM rock

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

ip

V(

ip)

Consider the OH stretch region

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar P

re

dis

so

cia

tio

n Y

ield

Ca

lcu

alte

dInte

nsity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Approximate by a harmonic treatment of the rock and the two identical OH stretches, coupled to the rock by a cubic term (qOH

2qrock) and analyze through an adiabatic approximations

The progression can be reproduced by applying a Franck-Condon approximation to these potential curves

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

E.L.Sibert, JCP 119, 10138 (2003)

vOH=0Two equivalent OH stretches

vOH=1; equilib. geom. shiftsIM rock

IM rock

Is this effect more general???

Broad bands are characteristic features of cyclic H-bond

arrangements in polypeptides

Can we come up with a simple model to describe the origin of these bands?

C. M. Leavitt, A. F. DeBlase, C. J. Johnson, C. T. Wolke, and M. A. Johnson.

Theoretical treatment:

From formate-water – frequency of OH changes with low-frequency vibrations

Can we model the spectrum by sampling the OH stretch spectrum based on the zero-point motions of the other vibrations?

Expt.

Harmonic

Start by carving out the relevant subsystem… O

O

O

OH

O

O

O

OH

ip

V(

ip)

vOH=0Two equivalent OH stretches

vOH=1; equilib. geom. shifts

Results for oxalate-H+: Results of model based

sampling the OH stretch spectrum using the zero-point motions of the other vibrations?

Simple picture picks up the overall breadth of the spectral feature

Allows us to investigate coupling between modes by exploring correlation between geometry and calculated harmonic frequencies

More in talk WG04 [Laura Dzugan]

O

O

O

OH

calc

expt

calc

exptO

O

O

OHD

So far we’ve seen examples of mechanical anharmonicity, what about the dipole

moment (e.g. electrical anharmonicity)

C. M. Leavitt, L. D. Jacobson, A. F. DeBlase, C. J. Johnson, C. T. Wolke, A. B. McCoy and M. A. Johnson, to be submitted to JPC-A.

Abstract book from 46th MSS (1991)

“Lehmann and Smith1 have illustrated that the intensities of overtone transitions are sensitive to details of the inner wall of the potential”K. K. Lehmann and A. M. Smith, J. Chem. Phys. 93, 6140 (1990)

Abstract book from 46th MSS (1991)

In that study, we focused on high XH stretch overtones and the results led us to focus on the role of the potential – here we will focus on stretch/bend combination bands and investigate contributions from the dipole surface

Some cautionary tales of “deficiencies” in harmonic picture

of molecular vibrations How should we think about anharmonic effects in molecular spectra? Electrical [non-linear terms in the dipole] Mechanical [higher order terms in the potential]

Are there simple models we can employ to anticipate and/or understand these effects?

Focus on five systems (with a few more along the way) Photoelectron spectrum of CHCl2-

Manifestations of anharmonicity in the formate.water complex

Investigating broad signatures of H-bonding Solvated H3O+ and insights gained about the origins of the

2100 cm-1 band in the spectrum of H2O(l)

H5+ - exciting into the dissociation coordinate

VHarmonic/μLinear

nq2

nq1

0.0 0.2 0.4 0.6 0.8 1.0

Energy (arb. units)

Types of anharmonicity:q 2

q1q1

q 2

Pote

nti

al

(mech

an

ical)

Dip

ole

(ele

ctri

cal)harmonic

V=k1 q12 + k2 q2

2 =d1 q1 + d2 q2

n1

n2

q 2

q1q1

q 2VHarmonic/μLinear

nq2

nq1

0.0 0.2 0.4 0.6 0.8 1.0

Energy (arb. units)

Effect of electrical anharmonicity:

Pote

nti

al

(mech

an

ical)

Dip

ole

(ele

ctri

cal)

V=k1 q12 + k2 q2

2 μ=d1 q1 + d2 q2

q 2

q1q1

q 2

VHarmonic/μNonlinear

nq2

nq1+q2

0.0 0.2 0.4 0.6 1.0

Energy (arb. units)

V=k1 q12 + k2 q2

2 μ=d1 q1 + d2 q2 + D12 q1q2

n1+n2

n2

n1

n1

n2

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Example of mechanical anharmonicity (intensity borrowing formate.HOH complex)

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

Photon Energy (cm-1)

Ar

Pre

diss

ocia

tion

Yie

ldC

alcu

alte

dIn

tens

ity

(a) HCO2¯·H2O harmonic

(b) HCO2¯·H2O expt

(c) HCO2¯·Ar2

(d) HCO2¯·Ar

νHOH bend

νCO asym

νOH νCH

νCO sym

νOH/IM rock 2νb νa+ νs

2νb νa+ νs

νCH

IM rock

Helen Gerardi, Andrew DeBlase and M. Johnson

IM rock

ANOTHER EXAMPLE: THE SPECTRUM OF H2O(L)

OH Stretch

librations HOH bend

* Bertie, J. E.; Lan, Z. D. Appl. Spectrosc. 1996, 50, 1047.

The spectrum of H2O(l) *

HOH bend + librations

0 1000 2000 3000 4000

Photon Energy, cm-1

Can we see these bands in clusters?

What do we think liquid water looks like?

Water bend frequency will depend on how tightly the OH bond is “tied” to the adjacent water molecule…

Solvated H3O+ provides a simpler model

Effects of solvation on the bend spectrum of solvated H3O+

1500 1800 2100 2400 2700 3000 3300 3600

Pre

dis

soci

atio

n Y

ield

Photon Energy, cm -1

d)

c)

b)

a)

a

e)

CHn

NNn

OHs stretch,

2n

OH a stretch,

2n

nOHX

2nHOH

nHOH

nOHN2+nON2

OHbend

2n

O+H

HH

Ar

ArAr

O+H

HH

CH4

CH4CH4

O+H

HH

N2

N2N2

O+H

HH

H2O

OH2H2O

ABM, T. Guasco, C. Leavitt, S. Olsen and MAJohnson, PCCP, (2012).

Effects of solvation on the bend spectrum of solvated H3O+

1500 1800 2100 2400 2700 3000 3300 3600

Pre

dis

soci

atio

n Y

ield

Photon Energy, cm -1

d)

c)

b)

a)

a

e)

CHn

NNn

OHs stretch,

2n

OH a stretch,

2n

nOHX

2nHOH

nHOH

nOHN2+nON2

OHbend

2n

O+H

HH

Ar

ArAr

O+H

HH

CH4

CH4CH4

O+H

HH

N2

N2N2

O+H

HH

H2O

OH2H2O

1. There is a band near 1900 cm-1 in all species

2. The band blueshifts with increased interaction strength

3. Its intensity also increases with interaction strength

4. Where does this intensity come from?

Tim Guasco, Solveig Olesen,,Christopher Leavitt and M. A. Johnson

Ar (degrees)

-180 -120 -60 0 60 120 180

q 1

-20

-10

0

10

20 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Ar (degrees)

-180 -120 -60 0 60 120 180

q 1

-20

-10

0

10

20 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

-120 -60 0 60 120 180

VAnh

Ar (degrees)

5500

7600

9700

11800

13900

16000q1

q2

VHarm

-20 -10 0 10 20

5500

7200

8900

10600

12300

14000

-20

-10

0

20

10

Potential and dipole surface for 3-Ar case

POTENTIAL LOOKS SEPARABLE

COUPLING IS IN THE DIPOLE SURFACE (ELECRICAL ANHARMONICITY)

Ar

q1

mx my

Ar (degrees)

-180 -120 -60 0 60 120 180

q 1

-20

-10

0

10

20 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Ar (degrees)

-180 -120 -60 0 60 120 180

q 1-20

-10

0

10

20 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

-120 -60 0 60 120 180

VAnh

Ar (degrees)

5500

7600

9700

11800

13900

16000q1

q2

VHarm

-20 -10 0 10 20

5500

7200

8900

10600

12300

14000

-20

-10

0

20

10

x xy

-180 -120 -60 0 60 120 180

-20

-10

0

20

Ar (degrees)

μx

q1

-1.00

-0.600

-0.200

0.200

0.600

1.00

O+

Ar

ArAr

HH

H

O+H

HH

Ar

ArAr

Ar= 0°

Ar= 180°

-180 -120 -60 0 60 120 180

Ar (degrees)

μy

-2.10

-1.26

-0.420

0.420

1.26

2.10

q1

q2

VHarm

-20 -10 0 10 20

5500

7200

8900

10600

12300

14000

-180 -120 -60 0 60 120 180

VAnh

Ar (degrees)

5500

7600

9700

11800

13900

16000

10

-20

-10

0

20

10

1500 1600 1700 1800 1900 2000 2100 2200

Photon Energy, cm-1

VHarm/μNonl

VHarm/μLin

VAnh/μNonl

VAnh/μLin

a

nHOH

H3O+

nHOH

H3O+

nHOH

H3O+

nHOH

H3O+ a

Figure 3Harmonic and anharomic spectrum

predicitions

α-band results from the electrical anharmonicity (in the (q1+q2)fAr contribution to the x-

component of the dipole moment)Can this be anticipated by single point calculations?

my

Calculated bend intensities at stationary points

Number of Ar atoms

Minimum Transition state

w(cm-1)

I (km mol-

1)

w(cm-1)

I (km mol-

1)

3H2O 1646 0.01 1663 2.69

3CH4 1690 0.08 1629 3.38

3N2 1723 0.19 1617 3.28

3Ar 1688 0.22 1666 2.69

bare 1690 1.00 N/A N/A

Why does the intensity of the bend is going down with

solvent strength?

0 100 200 300 400 500 600 700 800 900

0

20

40

60

80

100

120

140

I ben

d(k

m/m

ol)

Proton Affinity (kJ/mol)

NH3

H2OCH4

N2ArBare

HarmonicDipole

ElectricalAnharmonicity

Fixed charge model

charge sloshing

++

+

Effects of solvation on the bend spectrum of solvated H3O+

1500 1800 2100 2400 2700 3000 3300 3600

Pre

dis

soci

atio

n Y

ield

Photon Energy, cm -1

d)

c)

b)

a)

a

e)

CHn

NNn

OHs stretch,

2n

OH a stretch,

2n

nOHX

2nHOH

nHOH

nOHN2+nON2

OHbend

2n

O+H

HH

Ar

ArAr

O+H

HH

CH4

CH4CH4

O+H

HH

N2

N2N2

O+H

HH

H2O

OH2H2O

1. There is a band near 1900 cm-1 in all species

2. The band blueshifts with increased interaction strength

3. Its intensity also increases with interaction strength

4. Where does this intensity come from?

Tim Guasco, Solveig Olesen,,Christopher Leavitt and M. A. Johnson

What do we think liquid water looks like?

Water bend frequency will depend on how tightly the OH bond is “tied” to the adjacent water molecule…

Solvated H3O+ provides a simpler model

OH Stretch

librations HOH bend

* Bertie, J. E.; Lan, Z. D. Appl. Spectrosc. 1996, 50, 1047.

The spectrum of H2O(l) *

HOH bend + librations

0 1000 2000 3000 4000

Photon Energy, cm-1

Assignment is supported by cluster sizesnon-condon effects are clearly important

SO FAR WE’VE CONSIDERED COMBINATION BANDS, WHAT ABOUT OVERTONES?

NONE: The general expectation is that overtone intensities – decrease by ~ an

order of magnitude with each quantum of vibration (by ~100 between 1 0 and 2 0).

Does this hold for “floppy systems”?

EXAMPLE V. H5+

(MORE IN RG02)

Zhou Lin

Reported spectra (multi-photon)

200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Rela

tive Inte

nsi

ty

cm-1

320

379

470 815

940

1180

1399

17231952

* *

600 800 1000 1200 1400 1600 1800 2000

Rela

tive Inte

nsi

ty

cm-1

679 886 1059

1299

13571417

1505

1636

1767

H5+ H3

+ + H2

D5+ D3

+ + D2

Duncan, Asmis and co-workers JPC-Letters (2012)

Calculations put the shared proton frequency at 369 cm-1

Is such a long progression in a single vibration reasonable ? Can it be anticipated by calculation? What is it telling us about

H5+?

Note H5+ is another floppy molecule!

10 30 50 70

Short summary of calculations and results:*

Use Diffusion Monte Carlo to calculate the ground state and the v=1, 2 and 3 states in the shared proton stretch

The ground state is VERYlarge amplitude

Excited state calculations require a judicious choiceof coordinate**

**More on DMC/coordinates A. S. Petit TG02

R1

R2

*Z. Lin and ABM, JPC-A, ASAP for Wittig issue.

H3+

+H2

H2 +H3+

Excited state wave functions for H5+

Excitation of the shared proton drives the system further into the H2 + H3

+ dissociation channel

How do these numbers compare to the spectrum?

R1

R2

673 cm-1

369 cm-1 E0=7205 cm-1

983 cm-1

Z. Lin and ABM, JPC-A, ASAP for Wittig issue.

H3+

+H2

H2 +H3+

H3+

+H2

H2 +H3+

H3+

+H2

H2 +H3+

H3+

+H2

H2 +H3+

Reported spectra (multi-photon)

200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Rela

tive In

ten

sity

cm-1

320

379

470 815

940

1180

1399

17231952

* *

600 800 1000 1200 1400 1600 1800 2000

Rela

tive In

ten

sity

cm-1

679 886 1059

1299

13571417

1505

1636

1767

H5+ H3

+ + H2

D5+ D3

+ + D2

Duncan, Asmis and co-workers JPC-Letters (2012)

Calculations put the shared proton frequency at 369 cm-1

369983

713

Transitions reflect overtones in the shared proton stretch…

Is such a long progression reasonable?

v=1I = 1.00

v=3I = 0.06

v=5I = 0.02

2-d pseudo-linear triatomic calculation

Z. Lin and ABM, JPC-Letters, 3 6390 (2012).

G. S.

R1-R2 R1-R2 R1-R2 R1-R2

R1+

R2

R1+

R2

v=2

v=4

v=6

The next two states with correct symmetry carry comparable intensity to the v=5 state

The states that are being excited extend into the product channel for proton transfer

between H3+ and H2

v=1I = 1.00

v=3I = 0.06

v=5I = 0.02

2-d pseudo-linear triatomic calculation

Z. Lin and ABM, JPC-Letters, 3 6390 (2012).

G. S.

R1-R2 R1-R2 R1-R2 R1-R2

R1+

R2

R1+

R2

v=2

v=4

v=6

Outlooks and challenges When we think about vibrational spectra of “floppy”

systems we need to be aware of the prevalence of unexpected features that are not anticipated by harmonic pictures.

These can reflect both electrical and mechanical anharmonicity

Despite the large amplitude, often we can interpret the features through reduced dimensional pictures

The origins of the “association band” in the water spectrum are assigned to the electrical anharmonicity (non-condon effects)

For extremely large amplitude modes – high overtones may have unexpectedly large intensities

By identifying these transitions and understanding their origins we can gain insights into the nature of the bonding and vibrational dynamics of these important systems

Acknowledgements:ExperimentMark Johnson (Yale)

Tim GuascoChris LeavittChris JohnsonHelen GerardiAndrew DeBlase (effects of cubiccoupling terms - MG14)and the rest of the Johnson Lab

Carl Lineberger (CU) Kristen Vogelhuber

Scott Wrennand the rest of the Lineberger Lab

Michael Duncan (UGA) RECENT GRADUATES:

Samantha HorvathCharlotte Hinkle

Funding: NSF

Bernice Opoku-

Agyeman(Dynamicsof BrCN-

FE06)

Zhou Lin(H5

+ RG02)Laura Dzugan(Vib. Spectra

WG04)

Bethany Wellen

(BS 2013)

Meng Huang(X-.HOHRG13)

Andrew Petit(H3

+;DMCTG02)Jason Ford

A special thanks to Terry!