title: Proton tunneling in low dimensional cesium silicate LDS-1.
abstract: In low dimensional cesium silicate LDS-1 (monoclinic phase of CsHSi2O5), anomalous infrared absorption bands observed at 93, 155, 1210, and 1220 cm(-1) are assigned to the vibrational mode of protons, which contribute to the strong hydrogen bonding between terminal oxygen atoms of silicate chain (O-O distance = 2.45 Å). The integrated absorbance (oscillator strength) for those modes is drastically enhanced at low temperatures. The analysis of integrated absorbance employing two different anharmonic double-minimum potentials makes clear that proton tunneling through the potential barrier yields an energy splitting of the ground state. The absorption bands at 93 and 155 cm(-1), which correspond to the different vibrational modes of protons, are attributed to the optical transition between the splitting levels (excitation from the ground state (n = 0) to the first excited state (n = 1)). Moreover, the absorption bands at 1210 and 1220 cm(-1) are identified as the optical transition from the ground state (n = 0) to the third excited state (n = 3). Weak Coulomb interactions in between the adjacent protons generate two types of vibrational modes: symmetric mode (93 and 1210 cm(-1)) and asymmetric mode (155 and 1220 cm(-1)). The broad absorption at 100-600 cm(-1) reveals an emergence of collective mode due to the vibration of silicate chain coupled not only with the local oscillation of Cs(+) but also with the proton oscillation relevant to the second excited state (n = 2).
authors.affiliation: Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Iwamoto
authors.affiliation: Interdisciplinary Cluster for Cutting Edge Research, Center for Energy and Environmental Science, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan.
authors.forename: Dai
authors.initials: D
authors.lastname: Mochizuki
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan.
authors.forename: Shimon
authors.initials: S
authors.lastname: Osada
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Asakura
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kuroda
mesh_terms: D002586:Cesium / Q000737:chemistry; D006860:Hydrogen Bonding; D011522:Protons; D012824:Silicic Acid / Q000737:chemistry*; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D011522:Protons; D012824:Silicic Acid; D002586:Cesium