In order to realize electrostatic Stark deceleration of CH radicals and study cold chemistry, the fifth harmonic of a YAG laser is used to prepare CH(A2△) molecules through using the multi-photon dissociation of(CH3)2CO, CH3NO2, CH2Br2,and CHBr3 at ～ 213 nm. The CH product intensity is measured by using the emission spectrum of CH(A2△→ X2Π). The dependence of fluorescence intensity on laser power is studied, and the probable dissociation channels are analyzed. The relationship between the fluorescence intensity and some parameters, such as the temperature of the beam source, stagnation pressure, and the time delay between the opening of pulse valve and the photolysis laser, are also studied. The influence of three different carrier gases on CH signal intensity is investigated. The vibrational and rotational temperatures of the CH(A2△) product are obtained by comparing experimental data with the simulated ones from the LIFBASE program.
By using the dispersion theory instead of the Frhlich Hamiltonian,the polaron energy in a quantum dot with a parabolic confinement potential is investigated at finite temperatures.It is found that the self-trapping energy of the polaron decreases with the increasing temperature,and the temperature effect is more obvious in quantum dots with weaker confinement.
This paper proposes a scheme of axial triple-well optical dipole trap by employing a simple optical system composed of a circular cosine grating and a lens. Three optical wells separated averagely by～37 μm were created when illuminating by a YAG laser with power 1 mW. These wells with average trapping depth～0.5 μK and volume～74 μm3 are suitable to trap and manipulate an atomic Bose-Einstein condensation (BEC). Due to a controllable grating implemented by a spatial light modulator, an evolution between a triple-well trap and a single-well one is achievable by adjusting the height of potential barrier between adjacent wells. Based on this novel triple-well potentials, the loading and splitting of BEC, as well as the interference between three freely expanding BECs, are also numerically stimulated within the framework of mean-field treatment. By fitting three cosine functions with three Gaussian envelopes to interference fringe, the information of relative phases among three condensates is extracted.
A nonresonant two-photon absorption process can be manipulated by tailoring the ultra-short laser pulse.In this paper,we theoretically demonstrate a highly selective population of two excited states in the nonresonant two-photon absorption process by rationally designing a spectral phase distribution.Our results show that one excited state is maximally populated while the other state population is widely tunable from zero to the maximum value.We believe that the theoretical results may play an important role in the selective population of a more complex nonlinear process comprising nonresonant two-photon absorption,such as resonance-mediated (2+1)-three-photon absorption and (2+1)-resonant multiphoton ionization.
