Vacuum UV Polarization Spectroscopy of p-Terphenyl

p-Terphenyl is used as acomponent in a variety of optical devices. In this investigation, theelectronic transitions of p-terphenylare investigated by synchrotron radiation linear dichroism (SRLD) spectroscopyin the range 30000 – 58000 cm–1 (330 – 170 nm) on molecular samplesaligned in stretched polyethylene, thereby extending the region investigated bypolarization spectroscopy into the vacuum UV. The resulting partial absorbancecurves reveal that the vacuum UV band system with a maximum at 55000 cm–1(180 nm) is predominantly short axis-polarized. This result is of interest inthe optical applications of p-terphenyl,for example as a wavelength shifter. The observed polarization spectra arecompared with the results of quantum chemical model calculations. Convoluted versions of thetransitions predicted with the semiempirical ZINDOmethod and with the long range-corrected time-dependent density functional theory(TD–DFT) procedures TD–CAM-B3LYP, TD–LC-wPBE, and TD–wB97XD are insimilar qualitative agreement with the observed partial absorbance curvesthroughout the investigated spectral regions, while TD–B3LYP fails to predictqualitatively the spectrum of p-terphenylin the region above 40000 cm–1 (250 nm).