Photoionization dynamics of excited molecular states. Photoelectron angular distributions and rotational and vibrational branching ratios for H2C 1Πu,v=0–4

Photoelectron angular distributions

Angle-resolved photoelectron spectroscopy has been performed for more than 70 years in various guises, but recently its potential to help solve in detail problems in the photoionization dynamics and intramolecular dynamics of gas-phase molecules has been recognized. One key development has been the design of experiments in appropriate geometries to extract information that pertains to the molecular frame, another has been the development of imaging spectrometers, and a third is the use of ultrafast lasers to cause photoionization. In this review, which is aimed at experimentalists, simple expressions for photoelectron angular distributions (PADs) in various experimental geometries are given and their applications explained.

Nuclear magnetic resonance by measuring reaction yield of spin symmetry species

It is proposed that the nuclear magnetic resonance of sites which release dihydrogen can be obtained by measuring the branching fraction to the ortho and para forms. The motivation is to transform the sensitivity problem from that of detecting magnetization into the more tractable one of establishing the para and ortho content of free H2. It is shown with a density operator formalism that the para mole fraction reports directly on the zero-quantum coherence of the precursor and that other spin operators may be observed indirectly. Spectra are simulated for the case of a surface site from which H2 is released.