Laser Control of Chemical Reactions

Zare, Richard N.

doi:10.1126/science.279.5358.1875

Cited by 551 publications

(389 citation statements)

References 60 publications

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“…Laser-assisted chemical reaction control was investigated during the past years. 6 CO 2 laser is a typical energy source widely used in laser chemistry due to its high energy efficiency and high output power. However, common commercial CO 2 lasers only produce a fixed wavelength of 10.591 m, which cannot match the wavelengths required for effective vibrational resonant excitations.…”

Section: Introductionmentioning

confidence: 99%

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

Líu

Xie

Gao

et al. 2009

Journal of Applied Physics

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Wavelength-matched vibrational excitations of ethylene ͑C 2 H 4 ͒ molecules using a tunable carbon dioxide ͑CO 2 ͒ laser were employed to significantly enhance the chemical vapor deposition ͑CVD͒ of diamond in open air using a precursor gas mixture of C 2 H 4 , acetylene ͑C 2 H 2 ͒, and oxygen ͑O 2 ͒. The CH 2 -wag vibration mode ͑ 7 ͒ of the C 2 H 4 molecules was selected to achieve the resonant excitation in the CVD process. Both laser wavelengths of 10.591 and 10.532 m were applied to the CVD processes to compare the C 2 H 4 excitations and diamond depositions. Compared with 10.591 m produced by common CO 2 lasers, the laser wavelength of 10.532 m is much more effective to excite the C 2 H 4 molecules through the CH 2 -wag mode. Under the laser irradiation with a power of 800 W and a wavelength of 10.532 m, the grain size in the deposited diamond films was increased by 400% and the film thickness was increased by 300%. The quality of the diamond crystals was also significantly enhanced.

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Section: Introductionmentioning

confidence: 99%

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

Líu

Xie

Gao

et al. 2009

Journal of Applied Physics

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“…A major challenge is to connect these new insights with reaction dynamics and theories of chemical reaction. Another challenge is to relate novel molecular motions to methods to control molecular reactions; some approaches to control 56,57 clearly rely in part on knowledge of molecular motions, including bifurcation phenomena.…”

Section: Discussionmentioning

confidence: 99%

The Dance of Molecules: New Dynamical Perspectives on Highly Excited Molecular Vibrations

Kellman

Tyng

2007

Acc. Chem. Res.

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At low energies, molecular vibrational motion is described by the normal modes model. This model breaks down at higher energy, with strong coupling between normal modes and onset of chaotic dynamics. New anharmonic modes are born in bifurcations, or branchings of the normal modes. Knowledge of these new modes is obtained through the window of frequency-domain spectroscopy, using techniques of nonlinear classical dynamics. It may soon be possible to "watch" molecular rearrangement reactions spectroscopically. Connections are being made with reaction rate theories, condensed phase systems, and motions of electrons in quantum dots.

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“…Owing to the fast development of the computational tools the direct solution of the time-dependent Schroedinger equation has become one of the basic approaches to study the evolution of quantum systems. Thus, the wave packet propagation (WPP) method is successfully applied to time dependent and time-independent problems in gas-surface interactions, molecular and atomic physics, and quantum chemistry [1,2,3,4]. One of the main issues of the numerical approaches to the time-dependent Schroedinger equation is the representation of the wave function |Ψ(t) of the system.…”

Section: Introductionmentioning

confidence: 99%

The wave packet propagation using wavelets

Borisov

Shabanov

2002

Chemical Physics Letters

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It is demonstrated that the wavelets can be used to considerably speed up simulations of the wave packet propagation in multiscale systems. Extremely high efficiency is obtained in the representation of both bound and continuum states. The new method is compared with the fast Fourier algorithm. Depending on ratios of typical scales of a quantum system in question, the wavelet method appears to be faster by a few orders of magnitude.1. Owing to the fast development of the computational tools the direct solution of the time-dependent Schroedinger equation has become one of the basic approaches to study the evolution of quantum systems. Thus, the wave packet propagation (WPP) method is successfully applied to time dependent and time-independent problems in gas-surface interactions, molecular and atomic physics, and quantum chemistry [1,2,3,4]. One of the main issues of the numerical approaches to the time-dependent Schroedinger equation is the representation of the wave function |Ψ(t) of the system. Development of the pseudospectral global grid representation approaches yielded a very efficient way to tackle this problem. The discrete variable representation (DVR) [5] and the Fourier grid Hamiltonian method (FGH) [6,7] have been widely used in time-dependent molecular dynamics [1,2,8], S-matrix [9,10] or eigenvalue [11] calculations. The FGH method based on the Fast Fourier Transform (FFT) algorithm is especially popular. This is because for the mesh of N points the evaluation of the kinetic energy operator requires only NlogN operations and can be easily implemented numerically. In the standard FGH method the wave function is represented on a grid of equidistant point in coordinate and momentum space. It is well suited when the the local de Broglie wavelength does not change much over the physical region spanned by the wave function of the system [11]. There are, however, lot of examples where the system under consideration spans the physical regions with very different properties. Consider, for example, the scattering of a slow particle on a narrow and deep potential well. Despite the short wave lengths occur only in the well, in the FGH method they would determine the lattice mesh over entire physical space leading to high computational cost. In fact, pseudospectral global grid representation approaches are difficult to use in multiscale problems. This is why much of work has been devoted recently to the development of the mapping procedures in order to enhance sampling efficiency in the regions of the rapid variation of the wave function [8,11,12,13,14,15]. Though mapping procedure, based on the variable change x = f (ξ) is very efficient in 1D, it is far from being universal. One obvious drawback 1 is that it is difficult to implement in higher dimensions. In the case of several variables, there is no simple procedure to define the mapping functions f so that the lattice would be fine only in some designated regions of space. Next, the topology of the new coordinate surfaces can be different from that ...

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Laser Control of Chemical Reactions

Abstract: This copy is for your personal, non-commercial The following resources related to this article are available online at www.sciencemag.org

Cited by 551 publications

References 60 publications

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

Enhanced chemical vapor deposition of diamond by wavelength-matched vibrational excitations of ethylene molecules using tunable CO2 laser irradiation

The Dance of Molecules: New Dynamical Perspectives on Highly Excited Molecular Vibrations

The wave packet propagation using wavelets

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