1. 71st ISMS
UV Photodissociation Spectroscopy of Temperature-Controlled Hydrated Phenol Cluster Cation
Itaru KURUSU,
Reona YAGI,
Yasutoshi KASAHARA,
Haruki ISHIKAWA,
(Kitasato Univ.)

2. Microscopic hydration in molecular clusters
Owing to the development of the IR spectroscopic techniques, hydration structures of various clusters have been revealed .
The next stage for the investigation on the microscopic hydration is to understand the temperature effect.
n = 1
n = 1
n = 4
n = 2
n = 2
n = 3
n = 5
n = 4
n = 3
n = 5

3. Temperature effects on hydration structures
Low temperature
High temperature
Isomerization
fluctuation
The study of temperature effects on hydration structures in the gas phase should provide us with information about structural fluctuations in the bulk.

4. Spectroscopy of Temperature-controlled hydrated clusters
Temperature effects on microscopic hydration
Rare gas tagging
Cryogenically-cooled ion trap
Present study
Temperature-variable 22-pole ion trap apparatus
UV photodissociation spectroscopy of
hydrated phenol cation; [PhOH(H2O)n]+
n = 5
Spectroscopic information is available.

5. Temperature-variable 22-pole ion trap apparatus
Ref. Fujihara, et al. J. Phys. Chem. A 113, 8169 (2009).
Ishikawa, et al. Chem. Phys. Lett. 514 , 234 (2011).
1st Q-mass filter
2nd Q-mass analyzer
Photodissociation
laser
Octopole ion guide
22-pole ion trap (30 – 300 K)
Ionization laser
Pulsed nozzle

6. UV PD spectrum of [PhOH(H2O)5]+
TTrap = 20 K
Absorption of phenoxy radical
Vibronic bands
How many isomers?

7. Assignment of the bands of [PhOH(H2O)5]+
UV PD spectrum of [PhOH-TMA]+
Ref. N. Mikami, Bull. Chem. Soc. Jpn. 68, 683 (1995).
Same band pattern as [PhOH-TMA]+
There seems to be one isomer in our condition.

8. Temperature dependence of the PD spectra of [PhOH(H2O)5]+
TTrap = 20 K
Same pattern
TTrap = 20 K vs. 50 K
Additional band pattern appears at the high energy side.
At least two isomers or two groups of isomers exist in our observation.
Relative populations among these isomers depend on the temperature.
50 K
100 K
150 K
w/o trap

9. DFT calculation for [PhOH(H2O)5]+
Gaussian 09 wB97X-D/ G(d,p)
Cyclic with tail
140 cm-1
95 cm-1
Bi-cyclic
DE0 = 0 cm-1
112 cm-1
149 cm-1
Linear
DE0 = 400 cm-1
598 cm-1
649 cm-1

10. Temperature dependence
Relative population among the H-bond motifs
Entropic effect of the flexibility of the H-bond network
Similar dependence is reported for H+(MeOH)n
DE0 = 0 cm-1
Cyclic with tail
Linear
DE0 = 400 cm-1
Ref. Chem. Phys. Phys. Chem. 17, (2015).
Bi-cyclic
DE0 = 95 cm-1

11. Possible assignments Qualitative agreement!
Relative population among the H-bond motifs
TTrap = 20 K
Cyclic with tail
50 K
100 K
Linear
150 K
w/o trap
Qualitative agreement!

12. Summary
PD spectroscopy of temperature-controlled [PhOH(H2O)5]+ is carried out.
At least two isomers are identified.
Relative population among the isomers is examined based on the DFT calculation.
The spectral change observed is qualitatively considered.
Future
Extension of PD spectroscopy
0-0 region, the other sized clusters, IR
Detailed discussion based on both the measurements and calculations
Dynamical properties