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We study a cold atomic sample coherently driven into the five-level triple-Λ configuration for attaining a dynamically controlled triple photonic band-gap structure. Our numerical calculations show that three photonic band gaps with homogeneous reflectivities up to 92% can be induced on demand around the probe resonance by a standing-wave driving field in the presence of spontaneously generated coherence. All these photonic band gaps are severely malformed with probe reflectivities declining rapidly to very low values when spontaneously generated coherence is gradually weakened. The triple photonic band-gap structure can also be attained in a five-level chain-Λ system of cold atoms in the absence of spontaneously generated coherence, which however requires two additional traveling-wave fields to couple relevant levels. [ABSTRACT FROM AUTHOR]

We study the steady optical response of a five-level atomic system in the parametric region where resonant two-photon transitions are much stronger than far-detuned single-photon transitions. We find that the concurrent absorption of two weak probe fields can be well suppressed in a narrow spectral region to attain electromagnetically induced transparency (EIT) via quantum destructive interference between different two-photon transition pathways. To gain a deeper insight into relevant physics, we adiabatically reduce this five-level system with trivial single-photon transitions into a three-level system with vanishing single-photon transitions by deriving an effective Hamiltonian. The two systems have almost the same two-photon absorption spectra exhibiting typical EIT features but are a little different in fine details. This means that most characteristics of two-photon quantum destructive interference are reserved after the adiabatic elimination approximation. In addition, we verify by numerical calculations that the two-photon EIT spectra are insensitive to the dipole-dipole interaction of cold Rydberg atoms when the uppermost level has a high principle quantum number. [ABSTRACT FROM AUTHOR]

The dissociation of the molecular ion HD+ in moderate-intensity laser pulses is studied using the time-dependent quantum wave-packet method. Simulations of the time-of-flight (TOF) neutral atom spectra produced from dissociation of the v=10 vibrational state at a laser intensity of 1012W/cm² and from v=0 at the intensity of 5×1012W/cm² are calculated. Good agreement is found with previous experimental results [P. A. Orr et al., Phys. Rev. Lett. 98, 163001 (2007) and J. D. Alexander et al., J. Phys. B 42, 154027 (2009)]. Furthermore, the kinetic energy distribution of the dissociated fragments of molecular ion HD+ is studied within the moderate laser-intensity region from 1012 to 5×1012W/cm² by considering initial vibrational states from v=0 to 15. It is found that the above-threshold dissociation could be more obviously observed from the TOF spectra when the initial vibrational state is set as v=6 for a moderate-intensity femtosecond laser field. [ABSTRACT FROM AUTHOR]