Proton Stretch in H4O2+:
Effect of Ar
Jheng-Wei Li, Ying-Cheng Li, Kaito Takahashi and Jer-Lai Kuo
Institute of Atomic and Molecular Sciences,
Academia Sinica, Taipei, Taiwan
FC02 @ 70th OSU Int. Symp. on Mol. Spectroscopy,
University of Illinois Urbana-Champaign, USA, June/26/2015
Structural Evolution & Solvation of
OH radical in (H2O)n+, n=5~8
En-Ping Lu, Piin-Ruey Pan, Ying-Cheng Li and Jer-Lai Kuo
Institute of Atomic and Molecular Sciences,
Academia Sinica, Taipei, Taiwan
Ming-Kang Tsai
Dept of Chem., National Taiwan Normal University,
Taipei, Taiwan
RG02 @ 69th OSU Int. Symp. on Mol. Spectroscopy,
University of Illinois Urbana-Champaign, USA, June/19/2014
(H2O)n+ vs. H+(H2O)n
Mizuse, Kuo, Fujii, Chem. Sci., 2, 868 (2011)
IR Spectra of (H2O)n+, n=5~8
• Vib. band ~ 3200 cm-1 is assigned to fully solvated OH.
• Direct evidence of solvated OH radical for n ≥ 7.
Protonated Water Dimer Cation: H5O2+
IHB vibration = the doublet ~ 1000 cm-1
Full Dimensional Calculations on Joe Bowman’s PES@CCSD(T)/aTZ
Water Dimer Cation: H4O2+
H4O2+ Ar1
H4O2+ Ar2
Schaefer, H. F. et al. J. Phys. Chem. A 2009, 113, 13779
Johnson, M. A. et al. J. Phys. Chem. A 2009, 113, 4772
IHB vibration = Multiple intense peaks ~2000 cm-1
For IHB, is Argon relevant ?
Triplet rather than a single peak.
Outline
• Quick review on theoretical works
• Methodology
• Results
• Summary
7
Previous theoretical works - I
E. Kamarchik, O. Kostko, Joel M. Bowman, M. Ahmed, and A. I. Krylov
J. Phys. Chem. A, 113, 4772 (2009)
PES is obtained by MP2/aug-cc-pVDZ
(a) the outer bonds in H3O+
(b) the OO bond length,
(c) the HOH angle (i.e., of the outer OH bonds in H3O+)
(d) the dihedral angle corresponding to the orientation of the •OH moiety
Previous theoretical works - II
J. Chem. Phys., 132, 194311 (2010)
PES is obtained with EOM-IP-CCSD/aug-cc-pVTZ
IR spectra were done computed
Presence of Ar is not included
Normal Mode Approx. (NMA)
• A simple DVR along normal mode direction (approx.)
• PES obtained from ab initio cal. (no approx.)
Ù
V
Ù
é V (x )
0
0
1
ê
V (x2 )
0
ê 0
=ê
0
V (x3 )
ê 0
êë
Ù
ù
ú
ú
ú
ú
úû
Ù
T
é 2k -k 0
ê
-k 2k -k
=ê
ê 0 -k 2k
ê
ë
ù
ú
ú
ú
ú
û
Ù
• Diagonalize the H = T + V (no approx.)
• Intensities were calculated via Fermi Golden Rule (no approx.)
• We use harmonic grids on B3LYP/6-31+G(d,p)
Anharmonicity in H3O+..OH·
Harm.
Stretches(4D)
Bends+Stretches(6D)
11
Effect of Ar on H+ stretch (Structure)
1.072
2.490
1.035
2.507
1.028
2.522
1.199
2.396
0.991
Effect of Ar on H+ stretch (Vib. Spectra)
OH radical
Sym & Asym.
6D (3 d(OH) + H+ strech + 2 bends)
Effect of Ar on H+ stretch (Vib. Spectra)
OH radical
Sym & Asym.
6D (3 d(OH) + H+ strech + 2 bends)
Low-freq. vibrational modes
118cm-1
385cm-1
411cm-1
612cm-1
973cm-1
486cm-1
Possible origins of “Triplet”
114cm-1
113cm-1
965cm-1
961cm-1
What else? Location of Ar
n=1
n=2
1A
2B
1C
2A
E = -679.1286 Eh
ZPE = -679.0822 Eh
E = -1206.0989 Eh
ZPE = -1206.0521 Eh
E = -679.1265 Eh
ZPE = -679.0806 Eh
2C
1B
E = -679.1286 Eh
ZPE = -679.0822 Eh
E = -1206.1010 Eh
ZPE = -1206.0539 Eh
1A
1B
E = -1206.0989 Eh
ZPE = -1206.0521 Eh
Summary
• Vibrational spectra of H4O2+..Ar0,1&2 were computed.
• Strong coupling with two bending modes were found.
A few low freq – vibrational modes are important too.
• Vibrational feature ~ 2000 cm-1 is sensitive to the
position of Ar.
• Call for more exp. (Ne/He-tagged & 3 Ar-tagged)
& full dimensional calculations on high quality PES.