Laser ablation of nanoscale particles with 193 nm light
Laser interaction with nanoscale particles is distinct and different from laser-bulk material interaction, where a hot plasma is normally created. Here, we review our studies on 193 nm laser ablation of various nanoscale particles including NaCl, soot, polystyrene, and gold. The 20 ns laser beam with fluences up to 0.3 J/cm 2 irradiates nanoparticles in a gas stream at laser repetition rates from 10 to 100 Hz. The particle size distributions before and after irradiation are measured with a scanning mobility particle sizer (SMPS), and particle morphology is examined with electron microscopy. All the nanomaterials studied exhibit a similar disintegration pattern and similar particle formation characteristics. No broadband emission associated with particle heating or optical breakdown is observed. The nanoparticles formed after irradiation have a smaller mean diameter and an order of magnitude higher number concentration with a more spherical shape compared to the original particles. We use the photon-atom ratio (PAR) to interpret the laser-particle interaction energetics.
Photochemical interaction of polystyrene nanospheres with 193 nm pulsed laser light.
The photochemical interaction of 193 nm light with polystyrene nanospheres is used to produce particles with a controlled size and morphology. Laser fluences from 0 to 0.14 J/cm2 at 10 and 50 Hz photofragment nearly monodisperse 110 nm spherical polystyrene particles. The size distributions before and after irradiation are measured with a scanning mobility particle sizer (SMPS), and the morphology of the irradiated particles is examined with a transmission electron microscope (TEM). The results show that the irradiated particles have a smaller mean diameter ( approximately 25 nm) and a number concentration more than an order of magnitude higher than nonirradiated particles. The particles are formed by nucleation of gas-phase species produced by photolytic decomposition of nanospheres. A nondimensional parameter, the photon-to-atom ratio (PAR), is used to interpret the laser-particle interaction energetics.
Corporations and the Market for Law
The state competition for corporate law has long been studied as a distinct phenomenon. Under the traditional view, corporations are subject to a unique choice-of-law rule, the internal affairs doctrine (IAD). This rule is explained as a historical accident, or by the special logistics of the corporate contract. The resulting market for corporate law appears to have special characteristics, particularly including the dominance by the single state of Delaware. This paper challenges the traditional view. It shows that the corporate law market is best understood as a special application of the general market for law. Any differences are matters of degree rather than kind, and are explained by considerations underlying enforcement of all choice-of-law contracts rather than by factors unique to corporations. It follows that theories of corporate competition that ignore the broader law market context are incomplete, and that the competition for corporate law carries lessons for the law market generally. Moreover, the connection between the corporate and other law markets has implications for the nature of corporate law, the constitutional status of the IAD, the scope of the IAD, and for the relationship between state and federal law.