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The energy acquisition based on resonant excitations are of great importance in chemical and biological systems. Here, the intramolecular resonant absorption of polarized mid-infrared pulses by bulk water and surface water is investigated using molecular dynamics simulation. The consequent heating based on the OH stretching vibrations is found to be very prompt, achieving more than 100 K temperature jump under irradiation of a pulse with 1 ps width and maximum intensity of 0.5 V /nm. A general anisotropic phenomenon is manifested as a result of preferential resonant excitation of symmetric or asymmetric OH stretching vibration, depending on the relationships between the orientations of water molecules and the polarized direction of the pulse. In the case of water molecules with the preferred dipole orientation, constrained by applied static electric field or spacial confinement, parallel to the polarized direction of the pulses, the energy absorption is dominated by the symmetric stretching mode (around 99 THz), while in the perpendicular case, the asymmetric stretching mode (around 101 THz) is more efficient. Since orientated water molecules are prevalent in chemical and biological systems, these findings concerning orientation-dependent excitation of intramolecular vibrations are of special significance to understood the energy absorption and transition in relevant biochemical processes.

Geometric and electronic structures of W m Cu n (m + n ≤ 7) cluster have been systematically calculated by density functional theory at the generalized gradient approximation level for ground-state structures. W m Cu n clusters with n = 1, 3, 5 tend to form bipyramid structures, whereas WCu n favour planar shapes except for WCu 5. The configurations of W m Cu n clusters are more sensitive to the Cu atoms than the W atoms, while the average atomic binding energies and the total magnetic moments are determined by W atoms. The calculated second-order differences in energies and HOMO-LOMO energy gaps show pronounced odd-even oscillating behaviours. From the Mulliken electron population analysis, we found that Cu 4p and W 6p orbitals exhibit electronic charges and both Cu 4s and W 6s orbitals transfer electronic charges to the W 5d orbital, which lead to the extension of W-Cu bond lengths.