| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuP |
| Session: | Thin Films Poster Session |
| Presenter: | Natsumi Suzuki, Gakushuin University, Japan |
| Authors: | N. Suzuki, Gakushuin University, Japan G. Shimizu, Gakushuin University, Japan H. Nasu, Gakushuin University, Japan R. Tsuboi, Gakushuin University, Japan K. Yamakawa, Gakushuin University, Japan I. Arakawa, Gakushuin University, Japan |
| Correspondent: | Click to Email |
To reveal the nature of the hydrogen bond is important in understanding the physical properties of gaseous, liquid and solid water. Since water clusters are the simple hydrogen bond systems, our group has investigated their structures and vibrational states in a previous study using infrared absorption spectroscopy combined with the matrix isolation technique.1 We adopted CH4 as the matrix species because its infrared active property enables us to investigate the structure of the matrix itself. In a recent study, Kouchi et al. investigated amorphous ice (ASW) formed by the matrix sublimation method showing that the ice was different in structure from vapor-deposited ASW.2 Using an apparatus we have constructed for the purpose of spectroscopy in the range from 100 to 600 cm-1 under ultrahigh vacuum, we measured far-infrared spectra of matrix-sublimated ice (MSI) in addition to those in the mid-infrared region.
We used two independent apparatuses for far- and mid-infrared spectroscopy. Each apparatus was equipped with a continuous-flow helium cryostat on which the gold substrate is held by a copper holder and was evacuated to ultrahigh vacuum condition. A gas mixture of CH4 and H2O was deposited onto the substrate at 11 K. Spectra were recorded in the reflection configuration with a liquid-helium-cooled silicon bolometer for the far-infrared region and a HgCdTe detector for the mid-infrared one.
In the mid infrared spectrum at 10 K, we observed a sharp peak at 3010 cm-1 caused by the ν3 vibrational mode of CH4 and a broad band from 3080 to 3600 cm-1 assigned to bonded-OH stretching of ASW. As the temperature was increased, the CH4 peak decreased and the ASW band grew. At 60 K, where CH4 was completely desorbed from the substrate, the broad band changed in structure and showed a characteristic plateau extending from 3080 to 3600cm-1, which implies the formation of MSI. In the far-infrared region, a broad band ranging from 140 to 310 cm-1 also appeared at 60 K. In addition, these spectral features were almost invariant until 115 K. The drastic changes of the spectra corresponding the translation from ASW to crystalline ice were observed in both the mid- and far-infrared regions at 140 K. Comparing these spectra with those of vapor-deposited ASW in detail, we will discuss the structure of MSI.
References
[1] K. Yamakawa et al., AIP Advances 6, 075302 (2016).
[2] A. Kouchi et al., Chem. Phys. Lett. 685, 287 (2016).