Liquid crystal was discovered in 1888. However, it was only after the observation of dynamic scattering in nematics in 1968 and the subsequent application in displays that liquid crystal, as a field of research, has obtained its vitality and importance as we know it today.† Not surprisingly, it was in the early years of this modern era of liquid crystals that China ventured into this exciting “new” field.1-16

Liquid Crystal Research in China: 1970-1982

The method of moments for the simplified scattering and radiation on thin wire models can lead to the large-scale linear systems with non-Hermitian Toeplitz-like coefficient matrices. Since such reduced linear systems are typically dense and ill conditioned, iterative solvers are rarely considered to deal with the discretized linear systems in these electromagnetic model simulations. However, utilizing the Toeplitz-like structure of coefficient matrices, we can use the fast Toeplitz matrix-vector product (MVP) to refresh iterative solvers for the discretized linear systems. Compared with the traditional solvers, the fast numerical method can reduce the computational cost from to and the storage from to without using any lossy compression. Due to the Toeplitz-like structure of coefficient matrices, circulant preconditioners are considered to further accelerate the convergence of iterative solvers. Since the circulant matrices can be diagonalized via fast Fourier transforms (FFTs), the fast Toeplitz MVP is ...

Fast iterative solvers for numerical simulations of scattering and radiation on thin wires

A quantum statistical theory for a laser-driven anharmonic oscillator coupled to a system of many degrees of freedom by means of energy- and phase-dissipative mechanisms is presented. The theory is applied to the description of vibrational dynamics in an admolecule-surface system that are associated with desorption–dissociation processes. It is found that phase relaxation plays an important role in assisting the laser driving force to overcome the anharmonicity and/or detuning bottleneck. It is also shown that a shorter duration of the laser pulse is more efficient for depositing photon energy into the admolecule system.

Quantum statistical theory of vibrational dynamics in a laser-driven admolecule-surface system

In this article we will discuss what happens to a polyatomic molecule that is driven by a high-power, resonant, infrared laser. It is assumed that the molecules are in the gas phase, and our discussion centers around systems at low pressure so that we may focus our attention on one individual molecule immersed in the photon field of the laser. We will present detailed calculations simulating the response of two molecular species, SF6 and S2F10. In this introduction we will discuss briefly our (admittedly subjective) view of the current status of the multiphoton excitation-dissociation problem (mpe, mpd) with primary emphasis on SF6, the most studied molecule.

Vibrational Excitation in Polyatomic Molecules

Molecular correlation functions of homologous liquid crystals are calculated statistical mechanically from a generalized McMillan hamiltonian. It goes beyond the mean-field approximation and includes the nematic and smectic fluctuations on the same footing. The expressions obtained are valid for either the isotropic(I), nematic(N) or smectic A(A) phase and are equally applicable to I-N or I-A transitions. When specified to the isotropic phase the inverse correlation function G0 −1 shows a smooth “bending down” near TNI or TAI for all homologues in accordance with most experiments. The variation of the “degree” of the “bending down” with different members of a homologous series is in agreement with, e.g., the nCB and nOCB data of Muta et al. For 9CB and 11CB our G0 −1 curve, without “inflection”, “saturation” or “dip”, agrees with the experiments of Zhang et al., but not those of Coles and Strazielle, or Pouligny et al. Supercooling temperature T* [defined by G0 −1(T*) = 0] as function of molecula...

Theory of Homologous Liquid Crystals. II. Orientation Correlation Functions

Based on the theory of non-linear vibration and conception of uni-molecular reaction, we suggest in this article a physical model to describe the phenomena of instantaneous dissociation of polyatomic molecules interacting with an intense ir laser field. It is shown that there exists close and internal relationship between the dissociation threshold usually observed and the "jumping" processes occured inherently in nonlinear vibration. Taking the SFσ molecule as an example, the dissociation threshold, frequency "red shift" and the rotational compansation etc. are analyzed and evaluated. Good quantitative agreement between theoretical results and experimental observations is found.

Theory of multi-photon photo-dissociation of polyatomic molecules in an intense infrared laser field

The rigorous formula of Suzuki for correlation function of classical systems and Ising model is generalized and applied to the rotationally invariant Maier-Saupe Hamil-tonian of liquid crystals.The results show that the microscopic treatment of the correlation function and magnetic Cotton-Mouton coefficient by one of the authors is indeed correct within the approximation stated. The random phase approximation results of Vertogen and van der Meer is improved. A scheme to describe the thermodynamics of liquid crystals beyond the mean field approximation is proposed.

Generalized suzuki formula and its application in liquid crystals

A new integral equation for current distribution of a cylindrical antenna is de-rived. This is a one-dimensional Predholm equation of the second kind, and is different from the conventional Hallen equation in antenna theory. Emphasis is laid on the analysis of the current and magnetic field for an infinitely long antenna. It is found that our equation is more suitable for describing an actual antenna than the Hallen equation. Preliminary numerical computations for a finite antenna have been carried out. The results show that numerical computation using our equation is practical.

Fredholm integral equation of the second kind in antenna theory

Based on our previous work[5], in this paper, we discuss further the mechanism of maltiphoton dissociation of polyatomic molecules in an intense infrared laser field, and obtain non-linear equations which describe the coupling between molecular vibrational modes Taking SF6 molecule as an example, we calculate numerically the energy transfer time between modes, the Fermi resonance interaction, and the degree of mode excitation by laser field Finally, the dissociation rate of polyatomic molecule is discussed based on the uni-molecular reaction model, the theortical results are essentially in agreement with experiments

Feng Ke-An

Papers

Theory of multi-photon photo-dissociation of polyatomic molecules in an intense infrared laser field

Generalized suzuki formula and its application in liquid crystals

Fredholm integral equation of the second kind in antenna theory

Theory of multi-photon photo-dissociation of polyatomic molecules in an intense infrared laser field

The dissociation model of polyatomic molecule induced by infrared laser field