Electronic Spectroscopy and
Vibrationally Mediated
+
Photodissociation of Co (H2O),
+
+
Co (D2O) and Co (HOD) Systems
Abdulkadir Kocak
Geoff Austein-Miller
Prof. Ricardo B. Metz
Chemistry Department
Why Study Co+(H2O)?
 Strong non-covalent interaction
• Co+: 3d84s0 ground state; 3d74s1 excited state
• Bond strength:1.67±0.07 eV*
 How does binding to Co+ affect the H2O geometry and
bonding?
• CCSD(T):rO-H increases by 0.005 A; θ(H-O-H): increases by 3.3°
• How does this depend on the electronic configuration of metal?
 Geometry of the complex
• HF planar (C2v structure)
• B3LYP/6-311+G(3df,p) ~8degrees off planar (off from C2v)
• CCSD(T)/aug-cc-pVTZ~10degrees off planar (off from C2v)
* N. F. Dalleska, Kenji Honma, L. S. Sunderlin, P. B. Armentrout , JACS 1994 116 (8), 3519-3528
Chemistry Department
2
Apparatus Overview
Mass
Spectrometer
Make
Ions
Metal
rod
Laser
Mass
Select
Spectroscopy
Lasers
Accelerator Ion optics
RH,
H2O
He,
Ar
Detector
Mass gate
Reflectron
Ablation laser
R. B. Metz, Adv. Chem. Phys. 138, 331 (2008)
Chemistry Department
3
Experimental Results
Electronic Spectroscopy of
+
+
Co (H2O), Co (HOD) and
+
Co (D2O) Complexes
Chemistry Department
Photodissociation Spectrum of Co+(H2O)
Fragment Intensity
D0<13800 cm-1 (1.71 eV)
Dissociation
Onset
GIB value: 1.67±0.07 eV*
Strong non-covalent bond
d8 ground state
0.967 A
Frequency (cm-1)
Chemistry Department
107.5°
1.915 A
Bare water:
H-O-H:104.2°
O-H:0.962 A
* N. F. Dalleska, Kenji Honma, L. S. Sunderlin, P. B. Armentrout
JACS 1994 116 (8), 3519-3528
5
Photodissociation Spectrum of Co+(H2O)
Fragment Intensity
Sharp peaks: parallel bands
spacings ~320 cm-1
Multiple peaks: perpendicular bands
spacings ~300 cm-1
Two excited electronic states
Frequency (cm-1)
Chemistry Department
6
Vibrational Frequencies of Co+(H2O)
Frequency (cm-1)
Co+(H2O)
3680
Description
Frequency (cm-1)
H2O
3756*
1590
H-O-H asymmetric
stretch
H-O-H symmetric
stretch
H-O-H bend
577
In-plane bend
-
372
Co-O stretch
-
179
Out-of-plane bend
-
3606
3657*
1595*
All frequencies are at the B3LYP/6-311++G(3df,p) level and are scaled by 0.96.
*: Shimanouchi, T., Molecular Vibrational Frequencies, in NIST Chemistry WebBook, NIST
Chemistry Department
7
Relative Fragment (Co+) Yield
Co+(H2O), Co+(HOD) and Co+(D2O) Photodissoc. Spectra
a
b
c
d
H2O-HOD
(cm-1)
Co+(H2O)
a=0.3
Co+(HOD)
b=4.5
c=15
Co+(D2O)
d=16
Wavenumber (cm-1)
Chemistry Department
Assigned as Co-H2O stretch
8
Vibrational quantum numbering
c
a
d
b
The solid line, a fit to the observed shift, indicates that the peak at 13967 cm-1
corresponds to v’=0.
Chemistry Department
9
Photodissociation Spectrum of Co+(H2O)
Fragment Intensity
1
v’= 0
Assigned vibrational quantum
numbering in the electronic
excited state for v”=0
2
3
Frequency (ωe)= 325.4 cm-1
Anharmonicity (ωexe)= 3.6 cm-1
Frequency (cm-1)
Chemistry Department
10
Further scans for Co+(H2O)
0
1
0
2
1
3 4 5 6
0
14000
14000
15000
15000
Chemistry Department
16000
16000
2 3 4 5
1 2
3
17000
17000
6
To
ωe
ωexe
A
13967
325.4
3.6
B
(13501)
308.4
3.1
C
15854.9
328.7
2.4
D
16376
320.3
4.0
4 5
18000
18000
11
Co+(H2O) excited electronic states
4.00
Energy (eV)
3.00
2.00
1.00
0.00
1.60
2.10
2.60
3.10
Co-O bond length (Angstrom)
3.60
TD-DFT calculations of Co+(H2O) triplet states for different Co-O
Chemistry Department
12
Possible three electronic transitions
0.00
1.60
Chemistry Department
1.80
15123 cm-1
13735 cm-1
1.00
12122 cm-1
Energy (eV)
2.00
2.00
2.20
2.40
Co-O bond length (Angstrom)
2.60
13
Simulated electronic spectra
1
2
3
Intensity
0
11000
Shifted by
877 cm-1
12000
13000
14000
15000
16000
17000
Wavenumber (cm-1)
Chemistry Department
14
Summary And Future Work
Dissociation Energy of Co+(H2O) determined
Four excited electronic states have been observed
Vibrational progression in excited electronic states has
been assigned
We will carry out a rotational analysis
Chemistry Department
15
Experimental Results
Vibrational Spectroscopy
Vibrationally Mediated
Photodissociation of
+
Co (H2O) Complexes
Chemistry Department
Background Information about the techniques
Electronic Spectroscopy of cold molecules gives only
information about excited electronic states
Vibrational Spectroscopy gives information about
ground electronic state
D0 ≤ 13800
Frequency (cm- 1)
Co+(H2O)
3680
cm-1
Chemistry Department
Description
H-O-H asymmetric stretch
Frequency (cm-1)
H2O
3756*
3606
H-O-H symmetric stretch
3657*
1590
H-O-H bend
1595*
577
In-plane bend
-
372
Co-O stretch
-
179
Out-of-plane bend
17
Fragment Loss (% Depletion)
Vibrational Spectrum of Co+(H2O) using VMP
10
O-H symmetric stretch
of Co+(H2O)
O-H asymmetric stretch
of Co+(H2O)
v’=1
v’=0
13967 cm-1
fixed
0
v”=1
3612 and 3692 cm-1
v”=0
find
Depletion Experiment
-10
-20
O-H asymmetric stretch
of bare H2O
O-H symmetric stretch
of bare H2O
3600
3650
3700
3750
Frequency (cm-1)
The raw spectrum in yellow and the smoothed spectrum is in red.
Chemistry Department
18
Many Thanks To…
Prof. Ricardo B. Metz
Geoff Austein-Miller
Jennifer Silva Daluz
Gokhan Altinay
Wright Pearson
NSF for funding
Chemistry Department