Spectroscopic investigation of temperature effects on the hydration structure of phenol cluster cation Reona YAGI, Yasutoshi KASAHARA, Haruki ISHIKAWA Department of Chemistry, School of Science, Kitasato University The development of the IR spectroscopic techniques have revealed hydration structures of various clusters. The next stage for the investigation on the microscopic hydration is to understand the temperature effect. Microscopic hydration in molecular clusters n = 1 n = 2 n = 3 n = 4 n = 5 Low temperatureHigh temperature Temperature effects on hydration structures Isomerization among various isomers Structural fluctuation In the bulk The study of temperature effects on hydration structures in the gas phase should provide us with information about structural fluctuations in the bulk. This work 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(H 2 O) n ] + Spectroscopic information is available. Non-proton transferred and proton transferred forms may coexist. Absorption of phenol cation Absorption of phenoxy radical Ref. Sato and Mikami, J. Phys. Chem. 100, 4765(1996). n = 1 n = 2 n = 3 n = 4-6 Electronic spectra of [PhOH(H 2 O) n ] + Non-proton transferred and proton transferred forms may coexist. Absorption of phenol cation Absorption of phenoxy radical Ref. Sato and Mikami, J. Phys. Chem. 100, 4765(1996). n = 1 n = 2 n = 3 n = 4-6 Electronic spectra of [PhOH(H 2 O) n ] + Temperature dependence of the band profiles n = 4-6 Temperature-variable 22-pole ion trap apparatus He+H 2 O analyzer Electronic spectra of [PhOH(H 2 O) 5 ] + The spectrum of n = 5 is not so changed with the trapping time. There is one species. Rotational cooling is completed within 1 ms. Detect: n = 1 DFT calculation E 0 = 0.0 cm -1 E 0 = 29 cm -1 M05-2X/6-31++G(d,p) n = 5 E 0 = 83 cm -1 E 0 = 88 cm -1 E 0 = 108 cm -1 E 0 = 133 cm -1 E 0 = 183 cm -1 E 0 = 200 cm -1 Electronic spectra of [PhOH(H 2 O) 6 ] + The band shape clearly change with temperature cooling. There are two species. Their relative populations change with the temperature. Isomerization of n = 6 clusters during the cooling process. Detect : n = 1 DFT calculation E 0 = 0.0 cm -1 E 0 = 91 cm -1 M05-2X/6-31++G(d,p) n = 6 E 0 = 115 cm -1 E 0 = 162 cm -1 E 0 = 188 cm -1 E 0 = 280 cm -1 E 0 = 298 cm -1 E 0 = 336 cm -1 Summary To investigate the temperature effect on the microscopic hydration, Electronic spectra of [PhOH(H 2 O) 5,6 ] + under the temperature controlled condition n = 6 cluster Two species in the cooled condition Isomerization during the cooling process Measurements of electronic spectra of [PhOH(H 2 O) 6 ] + at various temperatures Identification of the structures of the isomers Application to the larger clusters Future 22-pole temperature-variable ion trap Temperature-variable 22-pole ion trap Temperature control of the ions Multiple collisions with temperature- controlled He Temperature range 23~300 K Thermal equilibrium between He and ions Electronic spectra of [PhOH(H 2 O) 5 ] + Detect : n = 1 n = 2 n = 3 n = 4 n = 1 non temperature-controlled Wavenumber / cm -1 Intensity n = 5 Infrared spectra of [PhOH(H 2 O) n ] +