Infrared spectroscopy of water clusters isolated in methane matrices: Effects of isotope substitution and annealing

Abstract

Using infrared-active solvents of CH4 and CD4 for matrix isolation, we measured infrared spectra of H2O and D2O clusters at 7 K. The solute-concentration dependence of the spectrum of H2O clusters in a CH4 matrix was investigated and was used for the peak assignment. Annealing procedures were found to promote the size growth of water clusters in methane matrices for all the combinations of (H2O, CH4), (H2O, CD4), (D2O, CH4), and (D2O, CD4). We also monitored the ν3 absorption due to methane to find the annealing-induced structural change only of solid CH4. The matrix effects on the vibrations of the clusters are discussed on the basis of “Tc plots”, where their frequencies are plotted as a function of the square root of the matrix critical temperature, Tc. The obtained plots assure the validity of the assignment of the cluster peaks.

VUV Photolysis of CH4–H2O mixture in methane-rich ices: Formation of large complex organic molecules in astronomical environments

“…All these complexes absorb in the same spectral region for the bending mode at 1600 cm -1 , but they have their characteristic spectral positions in the OH stretching region, ranging from 3800 to 3100 cm -1 . The formation of water clusters in CH 4 matrix is in good agreement with the studies carried out by Yamakawa et al 21 C 2 H 4 and C 2 H 2 absorbing strongly in the 500-1000 cm -1 , 1300-1500 cm -1 and 3200-2800 cm -1 spectral regions.…”

“…As mentioned earlier, the IR identification of CH 3 OH and CH 3 CH 2 OH has been based on previous studies [11][12][13][14][15][16][17][18][19][20][21][22][23] , however, propanol has been less studied and for this reason, we have investigated the behavior of the spectral position shifts of the C-O stretching vibration of CH 3 OH, CH 3 CH 2 OH and CH 3 CH 2 CH 2 OH in solid phase. In fact, as it will be discussed below, we have measured the C-O stretching peaks positions of solid CH 3 OH, CH 3 CH 2 OH, CH 3 CH 2 CH 2 OH at 1023.8, 1045.7, 1067.9 cm -1 , respectively.…”

D2O clusters isolated in rare-gas solids: Dependence of infrared spectrum on concentration, deposition rate, heating temperature, and matrix material

“…3,[9][10][11] Yamakawa et al recently presented infrared spectra of D 2 O clusters in addition to H 2 O ones isolated in methane matrices and plotted the frequencies of the bonded-OH and -OD stretching vibrations of the clusters in various matrices as a function of matrix T 1/2 c . 12 The frequencies in the matrices of rare gases and polyatomic molecules individually showed the almost linear dependence on T of (H 2 O) k and (D 2 O) k with k = 3-5 in the rare-gas solids were found to be smaller than those in the polyatomic molecular ones, as was predicted by Kihara. 13 Nevertheless, D 2 O clusters in matrices have not been fully investigated; in fact, infrared absorption peaks of (D 2 O) k with k = 5, 6 in solid Kr or k = 3-6 in solid Xe have not been reported.…”

“…The model describing the vibrational frequency shift of a solute caused by interaction with the surrounding solvent molecules was built by Volkenstein 34 and Buckingham. 35 In this model, the intermolecular potential, U 12 , between a solute, M 1 , and a neighboring matrix molecule, M 2 , is assumed to be described as a function of only the intermolecular distance, r. The magnitude of the vibrational-frequency shift of M 1 is approximately proportional to the absolute value of the 12 >| is approximated by…”

“…In these studies, matrices were annealed only at a temperature of 9 K for Ne, 3 30 K for Ar, 3 20 K for CH 4 , 12 and 17 K for CD 4 . 12 Yamakawa et al measured infrared spectra of H 2 O clusters in a two-dimensional H 2 matrix on a NaCl film with raising the substrate temperature, and quantitatively analyzed the cluster-size distribution. 17 In order for the detailed investigation of the pure effect of annealing on the cluster-size distribution, we should distinguish spectral changes irreversible with temperature from reversible ones such as the peak shift and broadening.…”