Cavity Ring-Down Spectroscopy of Anthracene, 9-Methylanthracene, and 2-Methylanthracene in Supersonic Expansion

Abstract

The S0–S1 absorption spectra of anthracene (C14H10), 9-methylanthracene (C15H12), and 2-methylanthracene (C15H12) are measured in the ultraviolet region between 330 and 375 nm (26,666 to 30,303 cm–1) with cavity ring-down spectroscopy in supersonic free-jet expansions of argon. The associated vibronic band systems and their spectroscopic assignments are discussed and compared to previous studies performed using fluorescence excitation and dispersed fluorescence techniques. Density functional theory (DFT) calculations were carried out to study the structures and evaluate the vibrational transitions of the ground and excited states. Time-dependent DFT calculations of the first electronic excited states and Franck–Condon factor calculations were carried out to assist in the assignment of the experimentally measured vibronic bands. The vibronic spectra obtained in absorption agree well with fluorescence excitation spectra in terms of peak positions but exhibit different relative band intensities. We find a very good match between experimentally obtained vibronic line positions and the peak positions of the quantum chemically calculated Franck–Condon excitation lines.

First Optical Constants of Laboratory-generated Organic Refractory Materials (Tholins) Produced in the NASA Ames COSmIC Facility from the Visible to the Near Infrared (0.4–1.6 μm): Application to Titan’s Aerosols

“…The plasma-induced chemistry results in the formation of larger gas-phase products and solid particles. The gas phase can be monitored with mass spectrometry (Ricketts et al 2011;Contreras & Salama 2013;Sciamma-O'Brien et al 2014;Raymond et al 2018;Dubois et al 2023) and cavity ring-down spectroscopy (e.g., Biennier et al 2006, Bejaoui & Salama 2019Bejaoui et al 2023). The solid particles can be deposited onto various substrates for ex situ analyses (e.g., Sciamma-O'Brien et al 2017;Gavilan Marin et al 2020, Gavilan et al 2022Sciamma-O'Brien & Salama 2020;Li et al 2022;Nuevo et al 2022).…”