在醋酸纤维素薄膜中四苯基卟吩的零声子线和局域模

ZERO-PHONON LINE AND LOCAL MODES OF TETRAPHENYLPORPHIN IN CELLULOSE ACETATE FILM

测量了酸醋纤维素(cellulose acetate)薄膜中四苯基卟吩(α,β,γ,δ-tetraphenyporphin,即TPP)的吸收光谱。分析了Gauss型的非均匀加宽的零声子线,用Huang-Rhys-Pekar(H-R-P)W_p(S,<m>)函数得到了H-R-P因子S～1.45.Raman散射实验证实了在TPP中有频率大约为1323cm^(-1)振动模的存在,同时也观测到了频率大约为1440cm^(-)的吡咯C-H弯曲模、1357cm^(-1)的吡咯=C-N拉伸振动模和频率大约为1155cm^(-1)的单取代苯拉伸振动模。

Because photochemical hole burning (PHB), population hole burning and photon echo are all performed on zero-phonon line (ZPL), it is useful to study ZPL and vibrational mode.We have obtained the absorption spectrum of tetraphenyporphin (TPP) in cellulose acetate film at room temperature which contains four bands peaking at 649, 594,552 and 516 nm respectively. They originated from the absorption transition of TPP, while host cellulose acetate does not contribute to this range of the absorption spectrum. The band centered at 649 nm is ZPL of TPP (0-0 transition) and its FWHM is about 2Cnm.By fitting the experiment data of the ZPL with Lorentzian and Gaussian line shapes respectively, it is shown that the ZPL is close to Gaussian. The ZPL is inhomogeneousely broadened.A vibrational mode of frequency 1323cm-1 was estimated from Fig.1(upper). According to Huang-RhyS-Pekar (H-R-P) Wp (S, <m>) functionwhere <m> is average phonon number, we calculated the so-called H-R-P factor s^1.45. Since l<s<5, the cellulose acetate matrix exhibited intermediate elec-tron-phonon coupling strength.In the Raman scattering excited by 514.5 nm line of Ar+ laser, A strong scattering at frequency 1328 cm- was observed. It was verified that there was really a vibrational mode of frequency 1323cm-1. Also, the pyrrole bending mode of frequency about 1440-1, the pyrrole =C-N stretch mode of frequency 1357cm-1 and mono-substituted benzene stretch mode of frequency 1155 cm-1 were observed.