Gerade/ungerade symmetry- breaking in HD at the n =2 dissociation limit
We report on a study of the I'1Πg outer well state of HD. Via a resonance-enhanced XUV + IR (extreme ultraviolet + infrared) excitation scheme, rovibronic levels (v = 0-2, J = 1-4) are populated and probed by pulsed lasers. Level energies are measured with an accuracy of 0.03 cm-1. Due to gerade-ungerade symmetry breaking, the long-range behavior of the I' potential in HD deviates from that of H2 and D2. When this deviation is taken into account a semi-empirical potential for the I'1Πg state may be constructed, resulting in better agreement with the observed level energies than derived from an adiabatic ab initio potential. With this new potential it is predicted that the I' well can sustain only 4 vibrational levels, with the v = 3 level having a binding energy of 1.38(3) cm-1. PACS Nos.: 33.80.Rv, 34.20.Cf, 33.20.Ni, 31.50.+w
Four‐wave sum mixing (130–180 nm) in molecular vapors
It is demonstrated that molecular vapors such as nitric oxide, bromine, and benzene can be used for resonantly enhanced four‐wave mixing into the vacuum ultraviolet. Coherent radiation in the 130–152‐nm region has been generated in nitric oxide, and continuous wavelength tunability achieved by pressure broadening the rotational structure at 10 atm. Estimates of the third‐order nonlinear susceptibility are shown to be consistent with the observed conversion efficiency in nitric oxide.
Persistence and Change in Minkowski Spacetime
There are famously two main metaphysics of persistence, namely three and four-dimensionalism. Both yield a particular solution to the so called puzzle of change. I argue that typical three-dimensionalist solutions to the puzzle face insurmountable difficulties even in the simplest relativistic setting, that of Minkowski spacetime