The Value of Different Experimental Observables: A Transient Absorption Study of the Ultraviolet Excitation Dynamics Operating in Nitrobenzene.

Excess energy redistribution dynamics operating in nitrobenzene under hexane and isopropanol solvation were investigated using ultrafast transient absorption spectroscopy (TAS) with a 267 nm pump and a 340-750 nm white light continuum probe. The use of a nonpolar hexane solvent provides a proxy to the gas-phase environment, and the findings are directly compared with a recent time-resolved photoelectron imaging (TRPEI) study on nitrobenzene using the same excitation wavelength [L. Saalbach et al., J. Phys. Chem. A 2021, 125, 7174-7184]. Of note is the observation of a 1/e lifetime of 3.5-6.7 ps in the TAS data that was absent in the TRPEI measurements. This is interpreted as a dynamical signature of the T2 state in nitrobenzene─analogous to observations in the related nitronaphthalene system, and additionally supported by previous quantum chemistry calculations. The discrepancy between the TAS and TRPEI measurements is discussed, with the overall findings providing an example of how different spectroscopic techniques can exhibit varying sensitivity to specific steps along the overall reaction coordinate connecting reactants to photoproducts.

Diving into the Details: Constructing a Framework of Random Call Components.

Random call is a randomized approach to select a student or group of students to share their thinking with the whole class. There are potential costs and benefits of random call in undergraduate courses, yet we lack insight about how this strategy is actually implemented and why instructors choose to use it. We interviewed 12 college biology instructors who use random call in courses with 50 or more students. Qualitative content analysis revealed why these instructors chose to use random call, the specific ways they implemented random call, and the reasoning behind their implementation. Instructors used random call to increase the diversity of voices heard in the classroom and to hold students accountable for working. Random call users showed concern about student anxiety and took specific steps to mitigate it. We break random call down into a series of components, identify the components that our participants considered most critical, and describe the reasoning underlying random call components. This work lays a foundation for future investigations of how specific random call components influence student outcomes, in what contexts, and for which students.