This paper solves numerically the full time-dependent Schrödinger equation based on the rigid rotor model, and proposes a novel strategy to determine the optimal time delay of the two laser pulses to manipulate the molecular selective alignment. The results illustrate that the molecular alignment generated by the first pulse can be suppressed or enhanced selectively, the relative populations of even and odd rotational states in the final rotational wave packet can be manipulated selectively by precisely inserting the peak of the second laser pulse at the time when the slope for the alignment parameter by the first laser locates a local maximum for the even rotational states and a local minimum for the odds, and vice versa. The selective alignment can be further optimised by selecting the intensity ratio of the two laser pulses on the condition that the total laser intensity and pulse duration are kept constant.
The adsorption of CO on the Nin cluster surfaces has been systematically investigated by density functional theory. The result indicates that the lowest energy structures of NinCO are generated with CO being adsorbed on Nin clusters, and the lowest energy structures of Nin clusters are not changed by adsorbing CO molecule, The chemisorption of CO on Nin cluster surfaces belongs to non-dissociative adsorption. The increased theoretical CO bond length of 0.1180-0.1214?nm (compared with 0.1138?nm) demonstrates the activation of the CO bond. Natural bond orbital analysis shows that the interaction between Ni atoms and CO molecule is primarily contributed by the hybridized molecular orbital within CO and 3d, 4s, 4p orbital of Ni atoms.
Geometric structures of MgnOn(n=2—8) clusters are optimized by using the generalized gradient approximation density functional theory. Energy, vibrational frequency and electronic properties have been calculated. The geometries of the global minima of MgnOn(n=2, 3) are ring-like. The three-dimensional structures of MgnOn(n≥4) may be built from Mg2O2 and Mg3O3 rings. The stability of clusters gained from obtuse O—Mg—O angles and much charge transfer. The transferred charge increases between Mg and O atoms with cluster size increasing, showing a tendency towards bulk charges. Mg3O3 and Mg6O6 clusters are shown to be more stable than neighboring ones by the investigations on vertical ionization potential, electron affinities and the energy gaps between the highest occupied and lowest unoccupied molecular orbitals.
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