Electron-phonon interaction of a dye dissolved in interstitial water

Fluorescence line narrowing spectroscopy has been performed in dye (Al-phth alocyanine tetrasulfonate) doped poly(acrylamide) (PAAm) gel in order to in vestigate the electron-phonon interaction of the dye dissolved in interstit ial water. The peak frequency of the one-phonon profile in this sample was found to be large when compared with other polymers such as poly(styrene) a nd poly(vinyl alcohol), and furthermore found to shift from 33 to 38 cm(-1) after hydrolysis. From Brillouin scattering measurements in several polyme rs, including the present polymer, we found that the Brillouin shift in PAA m gel is higher than that of other polymers and that the hydrolysis makes t he Brillouin shift even higher. This means that the elastic constant in PAA m gels is relatively large. This is argued to be due to the fact that the i nterstitial water confined in the network of PAAm gel stiffens the polymer structure. It should be noted that the sideband peak frequency of 38 cm(-1) is exactly the same as that in hyperquenched glassy water investigated by Small and coworkers. The temperature dependence of fluorescence line narrow ed spectrum shows that the electron-phonon interaction in this sample is re latively weak and that the zero phonon line is still discernible above 110 K. (C) 2000 Elsevier Science B.V. All rights reserved.