Quantum optimal control of the isotope-selective rovibrational excitation of diatomic molecules

黒崎 譲*; 横山 啓一

Chemical Physics, 493, p.183 - 193, 2017/08

AA2017-0230.pdf:8.02MB

https://doi.org/10.1016/j.chemphys.2017.07.003

塩化リチウム分子の同位体選択的振動回転励起の最適パルス波形を求めた。振動回転が基底準位にあるLiCl-35とLiCl-37の混合分子集団にレーザーパルスを照射し、LiCl-35(=0, =0)とLiCl-37(=1, =1)を生成する最適波形を最適制御理論により計算した。その結果、回転遷移だけを利用する方が効率よく選択励起を起こすことができることが示された。

Dynamic Stark効果による量子制御

黒崎 譲

しょうとつ, 12(4), p.114 - 125, 2015/07

http://www.atomiccollision.jp/collision/syoutotsu/15_1204s.pdf#page=19

近年の量子制御研究において、dynamic Stark効果(DSE)が重要キーワードの一つとなっている。DSEは静電場によるStark効果の振動電場への拡張バージョンといえるが、Stark効果自体はその発見から既に一世紀以上が経過しており目新しいものではない。しかしながら、最近のレーザー技術の飛躍的な進歩により、これまで未知であったDSEの数々の興味深い側面が明らかにされるにつけ、制御研究におけるDSEの重要性はますます高まってきている。本稿では、化学物理学におけるDSEによる量子制御研究の現状を概説するとともに、筆者らの最近の研究成果についても紹介する。

Dynamic discrimination of oriented molecules controlled with the nonresonant dynamic Stark effect induced by a single-cycle THz pulse

黒崎 譲; 赤木 浩; 横山 啓一

Physical Review A, 90(4), p.043407_1 - 043407_9, 2014/10

https://doi.org/10.1103/PhysRevA.90.043407

We theoretically propose a new control scheme of temporal wave-packet separation for oriented molecules, based on nonresonant dynamic Stark effect (DSE) in the dipole limit. In the scheme linearly-polarized single-cycle THz pulses are employed as control fields. In this work the proposed scheme is applied to the temporal wave-packet separation of the binary mixture of alkali halide isotopologues, CsI and CsI. We assume that before applying the control pulse one of the isotopologues is oriented along the field polarization direction and the other along the opposite direction and then they are electronically excited from the ground-state PEC to the excited-state counterpart. Numerical wave-packet propagations reveal that a THz pulse yields a temporal wave-packet separation of about 2 ps between the two isotopologue photodissociations.

Quantum optimal control pathways of ozone isomerization dynamics subject to competing dissociation; A Two-state one-dimensional model

黒崎 譲; Ho, T.-S.*; Rabitz, H.*

Journal of Chemical Physics, 140(8), p.084305_1 - 084305_11, 2014/02

https://doi.org/10.1063/1.4865813

We construct a two-state one-dimensional reaction-path model for ozone open cyclic isomerization dynamics. The model is based on the intrinsic reaction coordinate connecting the cyclic and open isomers with the O + O asymptote on the ground-state ' potential energy surface obtained with the high-level method. Using this two-state model time-dependent wave packet optimal control simulations are carried out. Two possible pathways are identified along with their respective band-limited optimal control fields; for pathway 1 the wave packet initially associated with the open isomer is first pumped into a shallow well on the excited electronic state potential curve and then driven back to the ground electronic state to form the cyclic isomer, whereas for pathway 2 the corresponding wave packet is excited directly to the primary well of the excited state potential curve. The simulations reveal that the optimal field for pathway 1 produces a final yield of nearly 100% with substantially smaller intensity than that obtained in a previous study using a single-state one-dimensional model. Pathway 2, due to its strong coupling to the dissociation channel, is less effective than pathway 1. The simulations also show that nonlinear field effects due to molecular polarizability and hyperpolarizability are small for pathway 1 but could become significant for pathway 2 because much higher field intensity is involved in the latter.

Theoretical study on isotope-selective excitation of diatomic molecules by a terahertz frequency comb

市原 晃; 松岡 雷士; 黒崎 譲; 横山 啓一

Proceedings of 10th Conference on Lasers and Electro-Optics Pacific Rim and 18th OptoElectronics and Communications Conference and Photonics in Switching 2013 (CLEO-PR & OECC/PS 2013) (USB Flash Drive), 2 Pages, 2013/06

光周波数コムにより、塩化リチウム分子を同位体選択的に回転励起させるためのコンピュータシミュレーションを実施した。振動回転状態の時間発展は、緊密結合法を用いて計算した。コムのスペクトル周波数をLiClの回転遷移周波数に一致させることにより、LiClとLiClに対して、LiClだけを高回転状態(J100)に励起することができた。使用したコムでは、振動状態励起は誘起されなかった。さらに、高回転状態のLiClの第二パルスによる解離過程を、波束法を用いて計算した。設定したパルスパラメータにより、振動回転状態(v=0, J=150)にあるLiClの約50%を解離することができた。これらの結果により、テラヘルツ領域の光学パルスを用いた二原子分子の同位体分離法の可能性を示した。

MRSDCI study on the low-lying electronic states of the lithium chloride molecule (LiCl)

黒崎 譲; 横山 啓一

Journal of Chemical Physics, 137(6), p.064305_1 - 064305_9, 2012/08

https://doi.org/10.1063/1.4742059

Potential energy curves (PECs) for the low-lying states of the lithium chloride molecule (LiCl) have been calculated using the MRSDCI method with the aug-cc-PVZ (AVZ) and aug-cc-PCVZ (ACVZ) basis sets, where = T, Q, and 5. First, we calculate PECs for 7 spin-orbit (SO)-free -S states, and then obtain PECs for 13 SO by diagonalizing the matrix of the electronic Hamiltonian plus the Breit-Pauli SO Hamiltonian. It is thus confirmed that to accurately predict the spectroscopic constants we need to include core-electron correlation in the CI expansion and use the basis sets designed to describe core-valence correlation, i.e., ACVZ.

Quantum control study of ultrafast isotope-selective vibrational excitations of the cesium iodide (CsI) molecule

黒崎 譲; 横山 啓一; 横山 淳

Computational and Theoretical Chemistry, 963(2-3), p.245 - 255, 2011/02

https://doi.org/10.1016/j.comptc.2010.10.044

We study, using quantum optimal control theory (OCT), isotope-selective vibrational excitations on the ground-state potential energy curve for the mixture of two pure ensembles for CsI and CsI. Initial states are set to the condition that both CsI and CsI are in the vibrational ground level, i.e., (, ) = (0, 0), and target states are set to three: (, ) = (0, 2), (0, 3), and (0, 4), where molecular orientations are fixed parallel to the field polarization vector. Three total times (i.e., pulse durations), T = 460,000 au, 920,000 au, and 1,840,000 au, are set in the calculations and nine cases for the combination of target state and total time are investigated. It is suggested from the computational results that even when T is short, high-yield transitions into energetically-separated target states are possible through excitations skipping over more than one vibrational level at a time with intense fields including high overtones.

Multilevel effect on ultrafast isotope-selective vibrational excitations; Quantum optimal control study

黒崎 譲; 横山 啓一; 横山 淳

Journal of Molecular Structure; THEOCHEM, 913(1-3), p.38 - 42, 2009/11

We demonstrate, using optimal control theory, that perfect isotope-selective molecular vibrational excitations on the ground-state potential curve in multilevel systems can be completed in much shorter time scales than those in two-level systems. We consider a gaseous isotopic mixture of cesium iodide (CsI and CsI) and, using two-level and multilevel systems, try to obtain electric fields that drive different isotopes into different vibrational levels. As a result, we find that in multilevel systems isotope-selective excitation processes can be controlled much faster, which we call multilevel effect. It is likely that this effect makes use of the large isotope shifts of higher vibrational levels than the lowest two.

Quantum optimal control of isomerization dynamics of a one-dimensional reaction-path model dominated by a competing dissociation channel

黒崎 譲; Artamonov, M.*; Ho, T.-S.*; Rabitz, H.*

Journal of Chemical Physics, 131(4), p.044306_1 - 044306_8, 2009/07

https://doi.org/10.1063/1.3185565

Quantum optimal control simulations have been carried out molecular isomerization dynamics of a one-dimensional (1D) reaction-path model involving a dominant competing dissociation channel. The 1D intrinsic reaction coordinate model mimics the ozone open cyclic ring isomerization along the minimum energy path that successively connects the ozone cyclic ring minimum, the transition state (TS), the open (global) minimum, and the dissociative O + O asymptote on the O ground-state 1A' potential energy surface. The molecular orientation of the modeled ozone is held constant with respect to the laser-field polarization and several optimal fields are found that all produce nearly perfect isomerization. The optimal control fields are characterized by distinctive high temporal peaks as well as low frequency components, thereby enabling abrupt transfer of the time-dependent wave packet over the TS from the open minimum to the targeted ring minimum.

Hydrogen-atom production channels of acetaldehyde photodissociation; Direct DFT molecular dynamics study

黒崎 譲

Journal of Molecular Structure; THEOCHEM, 850(1-3), p.9 - 16, 2008/02

https://doi.org/10.1016/j.theochem.2007.10.009

最低励起三重項状態(T)のポテンシャルエネルギー面(PES)上でのアセトアルデヒドの光分解における水素原子生成チャンネル: CDCHOCDCHO+D(1); CDCHOCDCO+H(2)について、密度汎関数理論(DFT)に基づく直接分子動力学計算を実施した。DFT法はB3LYPで、基底関数はcc-pVDZを用いた。計算の結果、生成した水素原子の平均の運動エネルギーは反応1, 2でそれぞれ18.3, 16.6kcal molであった。これらは、実験値[Kang et al., Chem. Phys. Lett. 434 (2007) 6]の半分から2/3の値であった。計算値が実験値に比べてかなり小さい理由は、反応1, 2の生成物側から見た障壁がB3LYP/cc-pVDZレベルでは小さく見積もられていることにある。しかしながら、ここでの計算結果は実験値と定性的には一致しており、これらの反応がTPES上で起こることを支持するものである。