Hiroaki Umeda

TWO-FREQUENCY IR LASER ORIENTATION OF POLAR MOLECULES. NUMERICAL SIMULATIONS FOR HCN

Abstract Using ab initio nuclear-coordinate-dependent dipole moments and polarizabilities, we study the orientation dynamics of HCN, by numerically solving the time-dependent Schrodinger equation, in the presence of a superposition of intense, linearly-polarized infrared laser pulses of frequency ω and 2ω. We show that polarizability acts in concert with permanent dipole moments to orient polar molecules, as opposed to alignment which occurs alone with a single laser frequency or one moment only (permanent or induced). Optimal orientation occurs for the field configuration E (t)= E 0 (t) cos ωt+0.5 cos 2ωt , where 2ω is resonant with a 0 → 1 vibrational transition and E 0 (t) is a picosecond pulse.

NUMERICAL SIMULATION OF THE ISOMERIZATION OF HCN BY TWO PERPENDICULAR INTENSE IR LASER PULSES

Isomerization of HCN is studied numerically for a laser excitation configuration of two perpendicular intense IR pulses. This scheme confines the molecule to a plane and promotes proton transfer along the curved reaction path. It is shown that internal rotation of the CN group enhances isomerization when compared to a fixed C≡N orientation model. Isomerization rates with rotation exceed those without rotation of the CN by about a factor of 3. Internal rotation also enhances dissociation and destroys phase control of the isomerization. It is found that at intensities I∼1013 W/cm2, maximum isomerization occurs with negligible dissociation for a 2 ps pulse excitation. Maximum isomerization is also found for one field frequency resonant with the CH bend frequency ωbend and the other perpendicular frequency at 2ωbend.

Fragment molecular orbital study of the electronic excitations in the photosynthetic reaction center of Blastochloris viridis

All electron calculations were performed on the photosynthetic reaction center of Blastochloris viridis, using the fragment molecular orbital (FMO) method. The protein complex of 20,581 atoms and 77,754 electrons was divided into 1398 fragments, and the two‐body expansion of FMO/6‐31G* was applied to calculate the ground state. The excited electronic states of the embedded electron transfer system were separately calculated by the configuration interaction singles approach with the multilayer FMO method. Despite the structural symmetry of the system, asymmetric excitation energies were observed, especially on the bacteriopheophytin molecules. The asymmetry was attributed to electrostatic interaction with the surrounding proteins, in which the cytoplasmic side plays a major role.

A theory of coherent control of reaction dynamics based on the optimization of a linear time-invariant system with complex variables

Abstract A theory of coherent control of reaction dynamics by pulse shaping is developed based on optimization of a linear time invariant system with complex variables. This theory is an extension of a previous control theory based on a linear time-invariant system for real variables [J. Chem. Phys., 100 (1994) 5646]. The theory is successfully applied to HCN → HNC in a one dimensional model. The isomerization takes place along a minimum energy path in which several vibrational levels below the potential barrier are selected as intermediate levels. Upper two levels of them are associated with tunneling dynamics. The effects of the tunneling dynamics on the coherent isomerization are discussed.

Multiphoton dissociation dynamics of hydrogen cyanide in nonstationary laser fields: important role of dipole moment function

Abstract Based on a multi-configuration self-consistent field and a nuclear wavepacket calculation, we present the effect of dipole moments on the infrared multiphoton dissociation dynamics of hydrogen cyanide in nonstationary laser fields. Use of a linear dipole moment depresses the dissociation ability of H+ CN as the laser intensity increases, compared with use of the real dipole moment function. The depression originates from the return of the nuclear wavepacket before the multiphoton dissociation. We analyze the time-dependent multiphoton dissociation yield with the dissociation yield at long time limit, dissociation rate constant and incubation time.

Quantum control of chemical reaction dynamics in a classical way

A simplified approach to quantum control of chemical reaction dynamics based on a classical, local control theory was developed. The amplitude of the control pulse is proportional to the linear momentum of the reaction system within the dipole approximation for the system-radiation field interaction. The kinetic energy of the system is the controlling parameter. That is, the reaction is controlled by accelerating the representative point on a potential energy surface before crossing over a potential barrier and then by deaccelerating it to the target after passing over the potential barrier. The classical treatment was extended to control of wave packet dynamics by replacing the classical momentum by a quantum mechanically averaged momentum on the basis of the Ehrenfest theorem. The present method was applied to a quantum system of a simple one-dimensional, double-well potential for checking its validity. A restriction of the applicability of the simplified method was also discussed. An isomerization of H...

Parallel Fock matrix construction with distributed shared memory model for the FMO‐MO method

A parallel Fock matrix construction program for FMO‐MO method has been developed with the distributed shared memory model. To construct a large‐sized Fock matrix during FMO‐MO calculations, a distributed parallel algorithm was designed to make full use of local memory to reduce communication, and was implemented on the Global Array toolkit. A benchmark calculation for a small system indicates that the parallelization efficiency of the matrix construction portion is as high as 93% at 1,024 processors. A large FMO‐MO application on the epidermal growth factor receptor (EGFR) protein (17,246 atoms and 96,234 basis functions) was also carried out at the HF/6‐31G level of theory, with the frontier orbitals being extracted by a Sakurai‐Sugiura eigensolver. It takes 11.3 h for the FMO calculation, 49.1 h for the Fock matrix construction, and 10 min to extract 94 eigen‐components on a PC cluster system using 256 processors.

Parallelization of multireference perturbation calculations with GAMESS

The quasi‐degenerate multireference second‐order perturbation theory (MRMP2) routines in the GAMESS suite of program codes have been parallelized using a distributed data interface (DDI). Two typical kinds of molecules were chosen for examination of parallelization speedup using one to eight PCs gathered as a cluster and connected by Fast Ethernet. The first example, in which total energies of several low‐lying electronic states have been obtained for niobium monohydride, give parallelization speedup of 7.15 when eight PCs were used as a cluster. The second example is the ground‐state total energy for a medium sized molecule, 4a,4b,8a,9a‐tetrahydro‐pyridino[1′,2′‐4,3]imidazo‐lidino[1,5‐a]pyridine. When distributed memory is employed, the parallelization speedup improves to 6.84 for the MRMP2 calculations when an eight‐PC cluster is used. These results demonstrate that our efforts to achieve the parallelization of MRMP2 routines have been successful.

Full Electron Calculation Beyond 20,000 Atoms: Ground Electronic State of Photosynthetic Proteins

A full electron calculation for the photosynthetic reaction center of Rhodopseudomonas viridis was performed by using the fragment molecular orbital (FMO) method on a massive cluster computer. The target system contains 20,581 atoms and 77,754 electrons, which was divided into 1,398 fragments. According to the FMO prescription, the calculations of the fragments and pairs of the fragments were conducted to obtain the electronic state of the system. The calculation at RHF/6-31G* level of theory took 72.5 hours with 600 CPUs. The CPUs were grouped into several workers, to which the calculations of the fragments were dispatched. An uneven CPU grouping, where two types of workers are generated, was shown to be efficient.

Applicability of a classical local control method to a quantum system

Quantum control of chemical reaction dynamics in a classical way derived in a previous study [J. Chem. Phys. 113 (2000) 3510] is extended by taking into account the distribution of the classical particles. Three types of control field expression are considered. The first type is designed to control a specific particle that is initially located at the center of the distribution in phase space. The second one is designed to control an effective particle with ensemble-averaged coordinates and their conjugate momentum. The third one is obtained by averaging over the fields controlling each particle of the ensemble. These are applied to a reaction system whose potential is of a one-dimensional double well. The third type of control field significantly improves the reaction yield in the presence of a bifurcation compared with the case in which the distribution is not considered. A control field for quantum wave packet dynamics is obtained by replacing the classical ensemble-averaged position and momentum with quantum mechanically averaged ones. The reaction control is explained in terms of a quantum state-to-state transition mechanism. This is proved by analyzing the time-resolved spectrum of the control field.