| Abstract
| - Nonphotochemical hole burning is used to measure the linear electron−phonon coupling, the temperaturedependence of the pure dephasing, and the zero-phonon hole growth kinetics of aluminum phthalocyaninetetrasulfonate (APT) in glassy water confined in pores (∼30 Å) of films of poly(2-hydroxyethyl methacrylate)(poly-HEMA). The hole burning properties of APT in the polymer are compared with those of APT inhyperquenched glassy films of water and ethanol. Below ∼8 K in the polymer, the dephasing, which isdominated by coupling to the intrinsic two-level systems (TLSint) of the glass, is found to be more similar tothat of APT in unannealed hyperquenched glassy water (HGW) films than in annealed HGW films. Thisshows, for the first time, that confinement does not lead to a significant decrease in the TLSint density. Athigher temperatures, dephasing due to exchange coupling with a pseudolocalized mode at 42 cm-1 becomesdominant. This coupling is due to diagonal quadratic electron−phonon coupling that leads to a change inmode energy upon electronic excitation of APT. The 42 cm-1 vibration is assigned to the transverse acousticmode of confined water. In HGW the energy of this mode is 50 cm-1. The interaction of APT with surface-bound water and the polymer surface also leads to reduction of the energy of the linearly coupled (Franck−Condon active) phonon mode from 38 cm-1 for HGW to 32 cm-1. Hole growth kinetics measurements forAPT in polymer saturated with D2O are compared with those in polymer saturated with H2O. In the heavywater the hole burning is 330 times slower. The equivalent factor for heavy HGW is 800. Thus, the mechanismof hole burning involves proton tunneling associated with the extrinsic two-level systems (TLSext) introducedby the dye. In contrast, dephasing data indicate that the coordinate of the TLSint is spatially extended andinvolves only small-amplitude motion of protons. Differences between the hole-burning properties of APT inpoly-HEMA and in HGW and hyperquenched ethanol are discussed in terms of the interactions of APT withbound (nonfreezable) water and the hydroxyethyl groups of the polymer.
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