Nie Yuxin

Resonant dip of two-photon ionisation and stimulated emission in laser-pumped magnesium vapour

An anomalous resonant dip of two-photon ionisation with 3s3p 1P as an intermediate state and a stimulated emission by the 3s4s 3S-3s3p 3P transition, at 518.37 nm following the pulsed laser excitation near the 3s2 1S-3s3p 1P resonance at 285.21 nm in magnesium vapour are observed and studied. The mechanism of the ionisation dip is attributed to formation and predissociation of the A 1 Sigma +u Mg2 dimer, which transfer the population from the laser-pumped 3s3p 1P level to 3s3p 3P levels. Re-excitation of the produced 3s3p 3P atoms and the subsequent radiative processes are presumed to explain the generation of stimulated emission. A theoretical model is employed to interpret the experimental phenomena.

New organic system for photon-gated persistent spectral hole burning

We report a new system of organic materials for photon-gated persistent spectral hole burning by donor-acceptor electron transfer: a tetrabenzoporphyrin derivative as donor and one of several aromatic cyanides as an acceptor in a poly (methyl methacrylate) (PMMA) host matrix. Up to 500% deep spectral holes in transmission were burnt and appeared very high hole burning efficiency.

Laser-induced double ionisation and fluorescence in magnesium vapour

Single and double ionisation of Mg I have been studied with a pulsed tunable UV laser in a heat-pipe oven. The resonant character of double ionisation as well as the Mg II fluorescence clearly show that double ionisation is essentially a two-step process, first creating the singly charged ion Mg+ which is then ionised to give the doubly charged ion Mg2+.

Generation of UV radiation at 285.4nm by four-wave mixing in magnesium vapor

The generation of UV radiation at 285.4nm by four-wave mixing in magnesium vapor is reported. A dye-laser radiation is focused into magnesium vapor and tuned to the resonance wavelength of the two-photon transition 3s2 0S1 - 3s4s 0S1. The dependence of the signal intensity at 285.4nm on Mg vapor density and incident laser power has been measured and the spectral behaviour has been studied.