Infrared Spectroscopy of Gas Phase Protonated CO2 Clusters

Gary E. Douberly, Allen M. Ricks, Brian W. Ticknor, and Michael A. Duncan

Department of ChemsitryDepartment of Chemsitry

University of GeorgiaUniversity of Georgiahttp://www.arches.uga.edu/~maduncan

Funding: National Science Foundation

Motivation

• Implementation of pulsed electric discharge source for protonated molecular clusters

• Infrared Spectroscopy of Mass-Selected Clusters

• Insight into proton environment with increasing cluster size. Structural Information

Experiment

Pulsed Discharge Cluster Source

0 250 500 750 1000 1250 1500 1750 2000 2250 2500

n=56

n=16

m/z

n=4H+(CO

2)n

300 psi1:10:100CO2 : H2 : (70/30) Ne/He

88 132 176 220 264 308 352 396 440

264 272 280 288 296 304 312 320 328

m/z

m/z

(n,m)

(1,6)

(2,5)

(3,4)

(4,3)

(5,2)

(6,1)

H+(CO2)n - Ar

m

(7,0)

300 psi1:10:20:100CO2 : H2 : Ar : (70/30) Ne/He

n=2

n=3

OPO OPA

1 crystalangle tuned

4 crystalsangle tuned

signal (not used)

idler

532 nm

1064 nm

KTPoscillator

KTAdiff. gen.

+ amp of idler beam

LiInS2

diff. gen.

Tunable4.2-10.1 m

2 crystalsangle tuned

Tunable mid-IR2.3-5.0 m

900 V

750 ns

LaserVision (Dean Guyer)

0 50 100 150 200 250 300 350

m/z

H+(CO

2)7

OPO On - Off

(cm-1) e ee D0

1 242.8 11.8 1130

2 182.4 3.6 2210

1800 2100 2400 2700 3000 3300 3600

Wavenumber (cm-1)

2+n

s

CO2H+

Ar-CO2H+

1+n

s

MP2 / aug-cc-pVTZ

s = 184.3 cm-1

D0 = 2400 cm-1

Protonated CO2 Dopfer O, …, Maier J; Chem Phys Lett. (1998) 296, 585.

1800 2100 2400 2700 3000 3300 3600

Wavenumber (cm-1)

Protonated CO2 Dimer

Monomer proton stretch

1000 1250 1500 1750 2000 2250 2500 2750 3000

Wavenumber (cm-1)

H+(CO2)

2-Ar

e = 153 cm-1 D

0 = 640 cm-1

MP2 / 6-311++G(2d,2p)

s = 127 cm-1

De = 660 cm-1

Protonated CO2 Dimer

(cm-1) H+(CO2)3 H+(CO2)3-ArDe Local 2630 790 De Global 3080 960

1000 1250 1500 1750 2000 2250 2500

Wavenumber (cm-1)

H+(CO2)3-Ar

loss of Ar

Protonated CO2 Trimer

Protonated CO2 Tetramer

1000 1250 1500 1750 2000 2250 2500

H+(CO2)3-Ar

loss of Ar

Wavenumber (cm-1)

H+(CO2)4-Ar

loss of Ar

Microsolvationof n=3 motif

44 88 132 176 220 264 308 352 396

2300 2350 2400 2450

0

1

2

3

4

5

6

7

8

Wavenumber (cm-1)

m/z

H+(CO2)7

Mode specific fragmentationdynamics

Summary

• Demonstration of pulsed electric discharge cluster source for argon tagged H+(CO2)n

• IR spectra from 950 to 2600 cm-1 reveals a rearrangement of Dimer structural motif for n=3

• Other protonated molecular clusters studied:

H+(CO)n , H+(H2O)n , H+(C3H6O)n , H+(O2)n , H+(N2)n

H+(C2H2)n , H+(C2H4)n, H3+(Ar)n, etc.

RF06

Protonated Acetylene and Ethylene Clusters

900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900

Wavenumber (cm-1)

Protonated Acetone Monomer and Dimer

Loss of Ar

eg.