Time-dependent photoemission from droplets: influence of size and charge on the photophysics near the surface

Photoemission from submicrometer droplets containing a mixture of dioctyl phthalate and dioctyl sebacate was investigated by femtosecond and nanosecond photoionization. Photoelectron spectra recorded after ionization with single 4.7 eV femtosecond or nanosecond laser pulses showed marked differences between the two cases. These differences were attributed to ionization of long-lived states which only occurred within the duration of the nanosecond pulse. The tentative assignment of the long-lived states to dioctyl phthalate triplet states is discussed. A nanosecond-femtosecond pump-probe scheme using 4.7 eV (pump) and 3.1 eV (probe) pulses was used to investigate the decay dynamics of these long-lived states. The dynamics showed an accelerated decay rate at higher dioctyl phthalate concentrations. Furthermore, the dependence of the decay dynamics on droplet size and charge was investigated. The decay of the long-lived states was found to be faster in smaller droplets as well as in neutral droplets compared with both positively and negatively charged droplets. Possible mechanisms to explain these observations and the dominance of contributions from the droplets surface are discussed.

Automated summary

In this study, photoemission from submicrometer droplets containing a mixture of dioctyl phthalate and dioctyl sebacate was investigated using femtosecond and nanosecond photoionization techniques. The results showed significant differences in the photoelectron spectra between ionization with nanosecond and femtosecond laser pulses, attributed to ionization of long-lived states within the duration of the nanosecond pulse. The decay dynamics of these long-lived states were investigated using a nanosecond-femtosecond pump-probe scheme, and an accelerated decay rate was observed at higher dioctyl phthalate concentrations. Additionally, the decay dynamics were found to be faster in smaller droplets and neutral droplets compared to charged droplets, suggesting the influence of droplet size and charge.