Gyeongsang National University, Jinju, Korea

Myong Yong Choi, Seung Jun Lee

Hydrated HCl Complexes, Hydrated HCl Complexes, (HCl)(HCl)mm(H(H22O)O)nn, in , in

Helium Nanodroplets:Helium Nanodroplets:HClHCl Stretching Modes Stretching Modes

The 65th International Symposium on Molecular Spectroscopy, June 21-25, 2010

University of Southern California, Los Angeles, CA 90089, U.S.A.Dimitry Skvortsov and Andrey F. Vilesov

( )m( )n

(-3.2)

(w/ ZPE in kJ/mol)MP2/aug-cc-pVDZ

(12.5)

(0.4)

(2.5)

(0)

n = 1 2 3 4

Calculations of Calculations of HCl-Water HCl-Water Clusters Clusters

The clear assignment of the hydrated HCl with four water molecules is not still available through spectroscopy.

Calculated spectra of HCl-(HCalculated spectra of HCl-(H22O)O)nn

1500 2000 2500 3000 3500 40000

500

Wavenumber (cm-1)

0

2000

0

2000

0

2000

0

2000

MP2/aug-cc-pVDZ

H3O+

b-OH

f-OH

HCl

b-OH (H2O)n

5 4 3 2

Science, 324, 1545 (2009)

Recent assignment of the Recent assignment of the S5S5 band in He droplets to band in He droplets to

HH33OO++-(H-(H22O)O)33-Cl-Cl-- +

-

Tiny droplets of acid. (Credit: Image courtesy of Ruhr-

Universitaet-Bochum)

S5S5

m/z=73

Recent assignment of the Recent assignment of the S5S5 band in He droplets to band in He droplets to

HH33OO++-(H-(H22O)O)33-Cl-Cl-- +

-

(HCl)m(H2O)n

n=4

m=1

n=10

S5S5

Science, 324, 1545 (2009)

Laser Depletion SpectroscopyLaser Depletion Spectroscopy

HClPick-up

Chamber

Main chamber

Closed-cyclerefrigerator

Nozzle

LN2 trap

Power meter

QuadrupoleX-Y-ZH2O

pick-up cell

Nd:YAG

1064 nm, 750 mJ, 7 ns

OPO/OPA

2050-6000 cm-1

≈ 1 m

-2 0 2 4 60

5

10

Sig

nal,

mV

Time, ms

Laser Pulse

m/e > 6

Overview Spectra in He dropletsOverview Spectra in He droplets

2600 2800 3000 3200 3400 3600 3800

Neat (HCl)m and (H2O)n

clusters

2600 2800 3000 3200 3400 3600 3800

wavenumber, cm-1

Mixed HCl and H2Oclusters

Skvortsov, Choi, Vilesov, unpublished 2007

HCl b-OH f-OH

S5S5

2650 2700 2750 2800 2850 2900 2950

<500>

<20>

<0.25>

<1.0>

<2.0>

<4.0>

Depletion signal

Wavenumber, cm-1

<8.0>

*

**

(e)

(g)

(d)

(f)

(c)

(b)(a)

1

234

55

1

2

34

55

6 6

IR Spectra of (HCl)IR Spectra of (HCl)mm Clusters Clusters

Skvortsov, Choi, Vilesov, JPCA 2007

m =

(HCl)1(H2O)1 0 1 2 3 4 5

MonomerDimer:

Dimer:

Trimer

Nor

mal

ized

sig

nal

Pressure, 10-5 mbar

Assignment of the clusters (HCl)Assignment of the clusters (HCl)mm(H(H22O)O)nn using pressure using pressure

dependence of the band intensity ratios: dependence of the band intensity ratios: IInn//II11

0.5 0.75 1 2.50.01

0.1

1

Slope = 2.8n = 4

Slope = 1.7n = 3

Lo

g(I

n/I

1)

Log(<H2O>)

Slope = 0.86n = 2

n is somewhat less than integerSub-linear dependence at large Z:- droplet size distribution,- decreasing of the droplet size- scattering of the beam- downstream pickup

According to Poisson dependence:

Log(In/I1) = (n-1)*Log(Z) + f(n)

n – Cluster sizeZ – Average number of collisions or pickup pressure

Water: difficult to reach zero pressure,Important, because otherwise Poisson does not workand interpretation of the pickup pressure results is ambiguous

2600 2800 3000 3200 3400 3600 3800

wavenumber, cm-1

Neat and mixed HCl and H2Oclusters

Skvortsov, Choi, Vilesov, unpublished 2007

HCl-H2O

*

2650 2700 2750 2800 2850 2900 2950

<500>

<20>

<0.25>

<1.0>

<2.0>

<4.0>

Depletion signal

Wavenumber, cm-1

<8.0>

*

**

(e)

(g)

(d)

(f)

(c)

(b)(a)

1

234

55

1

2

34

55

6 6

0 1 2 3 4 5

MonomerDimer:

Dimer:

Trimer

Nor

mal

ized

sig

nal

Pressure, 10-5 mbar

IR Spectra of (HCl)IR Spectra of (HCl)mm Clusters Clusters

Skvortsov, Choi, Vilesov, JPCA 2007

m =

0.25 0.5 0.75 1 2.5

0.01

0.1

1

Slope = 3.6m=5

Slope = 2.6m=4

Slope = 1.9m=3

Slope=0.97m=2

Lo

g(I

m/I

1)

Log(<HCl>)

m=1

Log(Im/I1) = (m-1)*Log(Z) + f(m)

Overview Spectra in He dropletsOverview Spectra in He droplets

2600 2800 3000 3200 3400 3600 3800

2600 2800 3000 3200 3400 3600 3800

wavenumber, cm-1

Mixed HCl and H2Oclusters

Neat (HCl)m and (H2O)n

clusters

Skvortsov, Choi, Vilesov, unpublished 2007

HCl b-OH f-OH

m =

4 2

3

12

n =

66

5 4 3 2

1

2

2

3+

Calculated spectra of HCl-(HCalculated spectra of HCl-(H22O)O)nn

1500 2000 2500 3000 3500 40000

500

Wavenumber (cm-1)

0

2000

0

2000

0

2000

0

2000

MP2/aug-cc-pVDZ

H3O+

b-OH

f-OH

HCl

b-OH (H2O)n

5 4 3 2

HCl-stretch bands in (HCl)HCl-stretch bands in (HCl)mm(H(H22O)O)nn clusters clusters

at different Z(at different Z(HClHCl))

1 2

0.1

1

2755 cm-1

2706 cm-1

2670 cm-1

2568 cm-1

2774 cm-1

Log

(Im/I

1)

Log(<HCl>)

Slope: 0.83m = 2

Slope: 1.72m = 3

S5S5

HCl-stretch bands in (HCl)HCl-stretch bands in (HCl)mm(H(H22O)O)nn clusters clusters

at different Z(at different Z(HH22OO))

1 2 30.1

1

2755 2706 2670 2774

slope = 0.06n = 1

slope = - 0.13n = 1

slope = - 0.06n = 1

Lo

g(I

n/I

1)

Log(<H2O>)

slope = 0.91n = 2

S5

S5

Assignment of the H-Cl stretching bands Assignment of the H-Cl stretching bands

2300 2400 2500 2600 2700 2800 2900

wavenumber, cm-1

2:2

HCl:H2O

2:04:0 3:0 2:0

In gasFarnik, Wiemann, Suhm, JCP 2003

S31:1

S2NA

S5NA

S4NA

S9NA

S6NA

S12:1

S82:1

S7NA

S101:2

2:1 overlapped with 4:01:1

2:11:2 or 2:2

3:13:1

??

??

S5S5

(HCl)m =

OO

XX

1.88 D

6.26 D

+ + +

_ _ _ _ _

+ +

2 1

0 10 20 30 40 50 60 70 80 90 1000.0

0.5

1.0

1.5

2.0

2.5

A(p

ara

.)/A(z

ero

)

electric field (kV/cm)

0o

90o

VTMA

+5o

2

0 10 20 30 40 50 60 70 80 90 100

electric field (kV/cm)

0o

90o

VTMA

+5o

1

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60 70 80 90

0.0

0.5

1.0

1.5

A(p

ara

.)/A(z

ero)

electric field (KV/cm)

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60 70 80 90

0.0

0.5

1.0

1.5

A(p

ara

.)/A(z

ero)

electric field (KV/cm)

+ + +

_ _ _ _ _

+ +

1

2

440 [NH2(AS)]420 [N9H]

800 [N1H]

310 [NH2(SS)]

290 [NH2(AS)]

730 [N7H]

470 [N1H]

830 [NH2(SS)]

Electric Field Dependence of Different DipolesElectric Field Dependence of Different Dipoles

1.88 D

6.26 D

6.26 D

1.88 D

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60 70 80 90

0.0

0.5

1.0

1.5

A(p

ara

.)/A(z

ero)

electric field (KV/cm)

310 [NH2(SS)]

290 [NH2(AS)]

M. Y. Choi and R. E. Miller, J. Am. Chem. Soc. 2006, 128, 7320.

0 10 20 30 40 50

0.6

0.8

1.0

1.2

1.4

1.6

I(fie

ld o

n)/I(

field

off)

Electric Field (kv/cm)

Predicted electric field dependence of Predicted electric field dependence of

the Hthe H33OO++-(H-(H22O)O)33-Cl-Cl- - bandband

S. Flynn, A. Morrison, T. Liang, G. Douberly, unpublished result (2010)

0 10 20 30 40 50

0.6

0.8

1.0

1.2

1.4

1.6

I(fie

ld o

n)/I(

field

off)

Electric Field (kv/cm)

EStark

ELaser

EStark

ELaserValues used to reproduce Experimental field dependence:p = 2.76 D, VTMA = 58.2O

p = 2.76 DVTMA = 58.4O

p = 4.22 DVTMA = 36.5O

Symmetric stretch

ConclusionsConclusions

- Observation of sharp infrared spectrum of [H(H2O)4]+Cl- seems illusive

- Calculated spectra may be at large variance with experiment

- Need for more Mutual Tests between Theory and Experiment

AcknowledgementsAcknowledgements

Andrey F. Vilesov Group at USC

GNU Laser Spectroscopy Lab.

m/z=73

Recent assignment of the Recent assignment of the S5S5 band in He droplets to band in He droplets to

HH33OO++-(H-(H22O)O)33-Cl-Cl-- +

-

(HCl)m(H2O)n

n=4

m=1

n=10

M=108: ??

(HCl)1(H2O)4

or (HCl)2(H2O)2

Science, 324, 1545 (2009)