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Ultrafast photorelaxation of uracil can be hindered by its natural RNA environment. Multiscale quantum dynamical simulations show that the wave packet can be trapped in the photoexcited electronic state, which could potentially lead to photodamage.

An elementary chemical reaction proceeds through two distinct conical intersections. Benzhydryl radicals are formed with a delay of 80 fs, cations after 125 fs. The optical signal increases more slowly due to planarization and solvation.

We demonstrate how the fast electron dynamics in molecules and hence the reaction of the system can be efficiently manipulated by controlling the temporal phase of an ultrashort laser pulse with attosecond precision.

UV-induced photolesions are studied in the visible and IR. While structural distortions of the DNA-backbone at the moment of light absorption are prerequisite for CPD-formation, strain from the backbone guides Dewar-formation.

We present a new dynamic continuum ansatz to describe the frictional force exerted on moving wave packets in a solvent cage. The solvent interferes on the femtosecond time scale, but decides the reaction outcome.

The vibrational dynamics of single molecular ions confined in a coulomb crystal are followed by 4 fs ultraviolet pulses. Theoretical calculations predicted the optimal laser parameters for a successful experiment under background free conditions. The ions are subject to internal heating, which has to be treated in the theory and handled in the experiment. Beyond the experiment the pump-probe scheme is extended by a coherent control scheme designed to suppress unwanted vibrational heating.

Our concept for a quantum computational system is based on qubits encoded in vibrational normal modes of polyatomic molecules. The quantum gates are implemented by shaped femtosecond laser pulses. We adopt this concept to the new species manganese pentacarbonyl bromide [MnBr(CO)5] and show that it is a promising candidate in the mid-infrared (IR) frequency range to connect theory and experiment. As direct reference for the ab initio calculations we evaluated experimentally the absorption bands of MnBr(CO)5 in the mid-IR as well as the related transition dipole moments. The two-dimensional potential-energy surface spanned by the two strongest IR active modes and the dipole vector surfaces are calculated with density-functional theory. The vibrational eigenstates representing the qubit system are determined. Laser pulses are optimized by multitarget optimal control theory to form a set of global quantum gates: NOT, CNOT, Π, and Hadamard. For all of them simply structured pulses with low pulse energies around 1 μJ could be obtained. Exemplarily for the CNOT gate we investigated the possible transfer to experimental shaping, based on the mask function for pulse shaping in the frequency regime as well as decomposition into a train of subpulses. [ABSTRACT FROM AUTHOR]

To achieve large population transfer to high vibrational levels in a selected ground-state mode of a polyatomic molecule [(Cr(CO)[SUB6]], we apply chirped femtosecond mid-infrared laser pulses at 2000 cm[SUP-1] to optimize vibrational ladder climbing as an energy deposition mechanism, which in turn controls the outcome of a unimolecular dissociation process. Its dependence on excitation parameters (frequency, intensity, chirp) is investigated and found to be in excellent agreement with a theoretical calculation. In particular, it is shown that optimizing vibrational ladder climbing allows for coherently controlled excitation even in a polyatomic molecule. [ABSTRACT FROM AUTHOR]

Laser pulses of moderate intensities with durations of either 1.5 ps or 120 fs were employed to excite the Na3 molecule to its electronic B state. Using a pump–probe technique the temporal evolution of the two-photon ionization signal could be resolved in real time. Different vibrational modes of the excited trimer are detected selectively. While the ps laser pulses yield preferential excitation of the slow pseudorotational mode with a period of 3 ps, the use of ∼10 times shorter pulses allows the trimer’s symmetric stretch mode with a 310–320 fs period for the first 5 ps to be observed. These complementary experimental results can be explained to a great extent by quantum dynamical simulations of the pump–probe experiments. The calculations are performed on three-dimensional ab initio potential energy and transition dipole surfaces. Thus all three vibrational degrees of freedom of the Na3 molecule are included in the theoretical treatment. The time-dependent wave-packet dynamics elucidate the effect of ultrafast state preparation on the molecular dynamics. Extensive theoretical calculations manifest the possibility of initiating the molecular dynamics dominantly in selected modes during a certain time span by variation of the pump–pulse duration. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Suitable molecules for quantum computing cannot be discussed in terms of anharmonicity and CNOT gates alone. The validity of the approximate approach [M. Zhao and D. Babikov, J. Chem. Phys.126, 204102 (2007)] is limited. Frequencies and anharmonicities cannot be used independent from the molecule. Hermite polynomials with the linear approximation for the dipole moment lead to oversimplified gates with potentially low intensities. [ABSTRACT FROM AUTHOR]