Pinning Down Small Populations of Photoinduced Intermediates Using Transient Absorption Spectroscopy and Time-Dependent Density Functional Theory Difference Spectra to Provide Mechanistic Insight into Controlling Pyridine Azo Dynamics with Protons.

In this work, the impact of protonation on the photoisomerization ( → ) and reversion ( → ) of three pyridine-based azo dyes () is investigated by using a combination of transient absorption spectroscopy and time-dependent density functional theory computed difference spectra. The photophysical behaviors of the dyes are altered by the addition of one or two protons. Protonation of basic pyridine nitrogens results in an ultrafast accelerated reversion mechanism after photoisomerization, while protonation of azo bond nitrogens restricts isomer formation entirely.

An Introduction to Processing, Fitting, and Interpreting Transient Absorption Data.

Transient absorption (TA) spectroscopy is a powerful time-resolved spectroscopic method used to track the evolution of excited-state processes through changes in the system's absorption spectrum. Early implementations of TA were confined to specialized laboratories, but the evolution of commercial turn-key systems has made the technique increasingly available to research groups across the world. Modern TA systems are capable of producing large datasets with high energetic and temporal resolution that are rich in photophysical information.

Longitudinal cardiac remodeling in collegiate American football players as assessed by echocardiography during their collegiate career.

Background: Studies on the longitudinal effects of intense physical training on cardiac remodeling are limited, especially in American collegiate football players.

Hypothesis: College-level American football training will result in remodeling in a pattern consistent of a sport with moderate static and dynamic demands with increases in both wall and chamber sizes.

Methods: We studied 85 American collegiate football players who underwent transthoracic echocardiogram (TTE) for asymptomatic or mild COVID-19-related illness and compared the changes in echo dimensions to their preparticipation screening TTE.

Ultra-fast excited-state dynamics of substituted -naphthalene azo moieties.

In this work we untangle the ultrafast deactivation of high-energy excited states in four naphthalene-based azo dyes. Through systematic photophysical and computational study, we observed a structure-property relationship in which increasing the electron donating strength of the substituent leads to longer lived excited states in these organic dyes and faster thermal reversion from the to configuration. In particular, azo dyes 1-3 containing less electron donating substituents show three distinct excited-state lifetimes of ∼0.