Photoisomerization action spectroscopy of the carbocyanine dye DTC in the gas phase

Abstract

Molecular photoisomerization plays a crucial role in diverse biological and technological contexts. Here, we combine ion mobility spectrometry and laser spectroscopy to characterize the photoisomerization of molecular cations in the gas phase. The target molecular ions, polymethine dye cations 3,3′-diethylthiacarbocyanine (DTC+), are propelled through helium buffer gas by an electric field and are photoisomerized by light from a tunable laser. Photoexcitation over the 450-570 nm range converts trans-DTC + to cis-DTC+, noticeably modifying the ions' arrival time distribution. The photoisomerization action spectrum, which has a maximum at 535 nm, resembles the absorption spectrum of DTC+ in so..