A Study of Ultrafast, Intense-field Photodynamics in Carbon Dioxide, Carbon Disulfide, and Select Substituted Benzenes

The study of the photodynamics of molecules in ultrashort pulses of intense radiation continues to be of interest. Electric field strengths in such pulses can approach or exceed the typical electric field strengths binding the electrons to the nuclear framework (ke/a20 ≈ 5 × 109 V/cm). The resulting excitation, ionization, and dissociation of molecular targets is of interest in many areas including attosecond science, femtochemistry, atmospheric science, high harmonic generation, and many other fields. This dissertation investigates the photoionization and photofragmentation behavior of carbon dioxide, carbon disulfide, and the substituted benzenes nitrobenzene, aniline, as well as toluene, phenol, and anisole in the gas phase under single-molecule conditions. Using 800 nm, 50-fs laser pulses at intensities ranging from 8 × 1012 W/cm2 to 3 × 1014 W/cm2, time-of-flight mass spectrometry data was collected for each target in the absence of the focal volume effect. For each systematic series, the effect of the different structural parameters are examined. We find many similarities between CO2 and CS2, but find differences beyond single ionization. Comparative analysis of aniline and nitrobenzene highlights how electron-donating versus electron-withdrawing substituents influence stability and fragmentation. In toluene, phenol, and anisole ionization dominates over fragmentation, but differences in yield slopes and REMPI signatures underscore the role of molecular substituents and their impact on intermediate state accessibility.Advisor: Cornelis Uiterwaal