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Biomedical subjects

K L Kompa

Publications and source records attributed to K L Kompa.

5 recordsLinked to original sources
PubMed2006

Chirp-driven vibrational distribution in transition metal carbonyl complexes.

In this theoretical study vibrational ladder climbing in transition metal carbonyl complexes, as a possible means to initialize chemical ground state reactions, and the resulting vibrational population distribution using chirped mid-infrared femtosecond laser pulses is investigated. Our model system is MnBr(CO)(5), a strong IR-absorber within an experimentally easily accessible wavelength region. Special emphasis is put on the perturbation due to additional vibrational modes, especially on one, which allows dissociation at low energies. The related potential energy surface for the three representative modes is calculated, whereon quantum dynamics calculations, including the laser-molecule interaction, are performed. No significant coupling could be detected, neither in the bound, nor in the dissociative region. Contrarily, we found a dynamical barrier even for energies high above the dissociation limit. Different vibrational population distributions after the laser excitation of the CO stretching mode could be generated in dependence of the chirp parameters. Based on these findings we simulated the laser excitation corresponding to an experiment by M. Joffre et al., Proc. Natl. Acad. Ssi. U. S. A., 2004, 101(36), 13216-13220, where coherent vibrational ladder climbing in carboxyhemoglobin was demonstrated and we could offer an explanation for an open question, concerning the interpretation of the spectroscopic data.

Journal Article↗
PubMed2005

Manganese pentacarbonyl bromide as candidate for a molecular qubit system operated in the infrared regime.

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, Pi, and Hadamard. For all of them simply structured pulses with low pulse energies around 1 microJ 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.

Journal Article↗
PubMed2001

Logic gates using high Rydberg states.

Connected logic gates can be operated on the levels of one molecule by making use of the special properties of high Rydberg states. Explicit experimental results for the NO molecule are provided as an example. A number of other options, including that of several gates concatenated so as to operate as a full adder, are discussed. Specific properties of high Rydberg states that are used are: their autoionization is delayed so that they can be distinguished from direct multiphoton ionization, during their long life such states also can decay by energy transfer to the molecular core in a way that can be controlled by the judicious application of very weak external electrical fields, and the Rydberg states can be detected by the application of an ionizing electrical field. The combination of two (or three) color photons with and without external weak fields allows the construction of quite elaborate logic circuit diagrams and shows that taking advantage of the different intramolecular dynamics of levels that differ by their excitation enables the compounding of logic operations on one molecular frame.

Journal Article↗
PubMed2001

A molecular logic gate.

We propose a scheme for molecule-based information processing by combining well-studied spectroscopic techniques and recent results from chemical dynamics. Specifically it is discussed how optical transitions in single molecules can be used to rapidly perform classical (Boolean) logical operations. In the proposed way, a restricted number of states in a single molecule can act as a logical gate equivalent to at least two switches. It is argued that the four-level scheme can also be used to produce gain, because it allows an inversion, and not only a switching ability. The proposed scheme is quantum mechanical in that it takes advantage of the discrete nature of the energy levels but, we here discuss the temporal evolution, with the use of the populations only. On a longer time range we suggest that the same scheme could be extended to perform quantum logic, and a tentative suggestion, based on an available experiment, is discussed. We believe that the pumping can provide a partial proof of principle, although this and similar experiments were not interpreted thus far in our terms.

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