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State-to-state Photoionization Dynamics of Vanadium Nitride by Two-color Laser Photoionization and Photoelectron Methods

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Chinese Journal of Chemical Physics 2013年第6期26卷 669-678,I0003页

作者： Huang Huang Zhi-hong Luo yih chung chang Kai-chung Lau C. Y. Ng Department of Chemistry University of California Davis CA 95616 USA Department of Biology and Chemistry Oty University of Hone Kong Kowloon Hone Kong China

We have conducted a two-color visible-ultraviolet （VIS-UV） resonance-enhanced laser pho- toionization and pulsed field ionization-photoelectron （PFI-PE） study of gaseous vana- dium mononitride （VN） in the total energy range of 56900-59020 cm-1. The VN molecules were selectively excited to single rotational levels of the intermediate VN（D3H0, v＇=0） state by using a VIS dye laser prior to photoionization by employing a UV laser. This two-color scheme allows the measurements of rovibronically selected and re- solved PFI-PE spectra for the VN＋（X2A; v＋=0, 1, and 2） ion vibrational bands. By simulating the rotationally resolved PFI-PE spectra, J＋=3/2 is determined to be the lowest rotational level of the ground electronic state, indicating that the symmetry of the ground VN＋ electronic state is 2A3/2. The analysis of the PFI-PE spectra for VN＋ also yields accurate values for the adiabatic ionization energy for the formation of VN＋（X2A3/2）, IE（VN）=56909.5＋0.8 cm-1 （7.05588±0.00010 eV）, the vibrational fre- quency wc＋=1068.0±0.8 cm-1, the anharmonicity constant wc＋Xe＋=5.8±0.8 cm-1, the rotational constants Be＋=0.6563±0.0005 cm-1 and ae＋=0.0069±0.0004 cm-1, and the equi-librium bond length, re＋=1.529A, for VN＋（X2A3/2）; along with the rotational constants Bc＋=0.6578i0.0028 cm-1 and a＋=0.0085±0.0028 cm-1, and the equilibrium bond length re＋=1.527A for VN＋（X2As/2）, and the spin-orbit coupling constant A=153.3±0.8 cm-1 for VN＋（X2/k5/2,3/2）. The highly precise energetic and spectroscopic data obtained in the present study are valuable for benchmarking the predictions based on state-of-the-art ab initio quantum calculations.

关键词： Vanadium nitride Vanadium nitride cation Photoionization dynamics Two- color photoionization Pulsed field ionization-photoelectron Ionization energy Bond disso- ciation energy

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O(3P0,1,2,1D2) yield ratio measurement in VUV photodissociation of O2

O(3P0,1,2,1D2) yield ratio measurement in VUV photodissociat...

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第十五届全国化学动力学会议

作者：刘凯 yih chung chang Konstantinos S.Kalogerakis Tom G.Slanger Bing Zhang William M.Jackson Cheuk Yiu Ng Department of Chemistry University of California State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of Sciences Physical Sciences Division SRI International

The quantum yield of a VUV-induced photodissociation is defined as the ratio of the number of dissociative fragment created to the number of photons absorbed. Neutral photodissociation cross sections often remain significant for several electron volts above the ionization threshold and may be composed of contributions from both direct and indirect processes. We developed a method to measure the yield ratios of O atoms in different spin-orbital state, using VUV-VUV pump-probe lasers and the time-sliced velocity-map-imaging photoion(VMI-PI) method. Combining the quantum dissociation cross section data[1], we calculated the quantum yield for O P, P, P, D and S in VUV photodissociation of O(HП, v’=2) is 0.24(2), 0.31(2), 0.26(2), 0.38(2), 0, respectively.

关键词： superexcited oxygen quantum yield VUV photodissociation

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Extensions of nonlinear error propagation analysis for explicit pseudodynamic testing

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Earthquake Engineering and Engineering Vibration 2009年第1期8卷 77-86页

作者： Shuenn-yih chang Department of Civil Engineering Taipei University of Technology NTUT Box 2653 Chinese Taipei 106-08

Two important extensions of a technique to perform a nonlinear error propagation analysis for an explicit pseudodynamic algorithm （chang, 2003） are presented. One extends the stability study from a given time step to a complete step-by-step integration procedure. It is analytically proven that ensuring stability conditions in each time step leads to a stable computation of the entire step-by-step integration procedure. The other extension shows that the nonlinear error propagation results, which are derived for a nonlinear single degree of freedom （SDOF） system, can be applied to a nonlinear multiple degree of freedom （MDOF） system. This application is dependent upon the determination of the natural frequencies of the system in each time step, since all the numerical properties and error propagation properties in the time step are closely related to these frequencies. The results are derived from the step degree of nonlinearity. An instantaneous degree of nonlinearity is introduced to replace the step degree of nonlinearity and is shown to be easier to use in practice. The extensions can be also applied to the results derived from a SDOF system based on the instantaneous degree of nonlinearity, and hence a time step might be appropriately chosen to perform a pseudodynamic test prior to testing.

关键词： nonlinear error propagation explicit pseudodynamic algorithm stability condition step-by-step integration procedure step degree of nonlinearity

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Improved formulations of the CR and KR methods for structural dynamics

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Earthquake Engineering and Engineering Vibration 2018年第2期17卷 343-353页

作者： Shuenn-yih chang Department of Civil Engineering Taipei University of Technology

Although the Chen-Ricles（CR）method and the Kolay-Ricles（KR）method have been applied to conduct pseudodynamic tests,they have both been found to have some adverse numerical properties,such as conditional stability for stiffness hardening systems and an unusual overshoot in the steady-state response of a high-frequency *** improved formulation for each method can be achieved by using a stability amplification factor to boost the unconditional stability range for stiffness hardening systems and a loading correction term to eliminate the unusual overshoot in the steady-state response of a high-frequency *** details for developing improved formulations for each method are shown in this work.

关键词： conditional stability overshoot structural nonlinearity stability amplification factor loading correction term

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Nonlinear performance of classical damping

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Earthquake Engineering and Engineering Vibration 2013年第2期12卷 279-296页

作者： Shuenn-yih chang Department of Civil Engineering Taipei University of Technology

The performance of a classical damping matrix, constructed either from the use of initial structural properties or current structural properties, in the step-by-step solution of a nonlinear multiple degree of freedom （MDOF） system is analytically evaluated. The analytical results are confirmed by numerical examples. Consequently, some conclusions are drawn from these analytical results that might be considered as rough guidelines for practical applications. It is found that a classical damping matrix constructed from initial structural properties is adequate for practical applications, since it has approximately the same damping effect as obtained by current structural properties and is more efficient in terms of computing.

关键词： classical damping nonlinear dynamic analysis integration method

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Selection of time step for pseudodynamic testing

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Earthquake Engineering and Engineering Vibration 2011年第3期10卷 437-451页

作者： Shuenn-yih chang Department of Civil Engineering Taipei University of Technology (NTUT)

Although the step degree of nonlinearity has been introduced to conduct basic analysis and error propagation analysis for the pseudodynamic testing of nonlinear systems, it cannot be reliably used to select an appropriate time step before performing a pseudodynamic test. Therefore, a novel parameter of instantaneous degree of nonlinearity is introduced to monitor the stiffness change at the end of a time step, and can thus be used to evaluate numerical and error propagation properties for nonlinear systems. Based on these properties, it is possible to select an appropriate time step to conduct a pseudodynamic test in advance. This possibility is very important in pseudodynamic testing, since the use of an arbitrary time step might lead to unreliable results or even destroy the test specimen. In this paper, guidelines are proposed for choosing an appropriate time step for accurate integration of nonlinear systems. These guidelines require estimation of the maximum instantaneous degree of nonlinearity and the solution of the initial natural frequency. The Newmark explicit method is chosen for this study. All the analytical results and the guidelines proposed are thoroughly confirmed with numerical examples.

关键词： pseudodynamic test nonlinear error propagation instantaneous degree of nonlinearity step degree of nonlinearity

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Nonlinear evaluations of unconditionally stable explicit algorithms

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Earthquake Engineering and Engineering Vibration 2009年第3期8卷 329-340页

作者： Shuenn-yih chang Department of Civil Engineering Taipei University of Technology

Two explicit integration algorithms with unconditional stability for linear elastic systems have been successfully developed for pseudodynamic testing. Their numerical properties in the solution of a linear elastic system have been well explored and their applications to the pseudodynamic testing of a nonlinear system have been shown to be feasible. However, their numerical properties in the solution of a nonlinear system are not apparent. Therefore, the performance of both algorithms for use in the solution of a nonlinear system has been analytically evaluated after introducing an instantaneous degree of nonlinearity. The two algorithms have roughly the same accuracy for a small value of the product of the natural frequency and step size. Meanwhile, the first algorithm is unconditionally stable when the instantaneous degree of nonlinearity is less than or equal to 1, and it becomes conditionally stable when it is greater than 1. The second algorithm is conditionally stable as the instantaneous degree of nonlinearity is less than 1/9, and becomes unstable when it is greater than 1. It can have unconditional stability for the range between 1/9 and 1. Based on these evaluations, it was concluded that the first algorithm is superior to the second one. Also, both algorithms were found to require commensurate computational efforts, which are much less than needed for the Newmark explicit method in general structural dynamic problems.

关键词： explicit integration algorithms unconditional stability pseudodynamic algorithm nonlinear system instantaneous degree of nonlinearity

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A family of explicit algorithms for general pseudodynamic testing

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Earthquake Engineering and Engineering Vibration 2011年第1期10卷 51-64页

作者： Shuenn-yih chang Chi-Wei Hsu Department of Civil Engineering Taipei University of Technology (NTUT) NTUT Box 2653

A new family of explicit pseudodynamic algorithms is proposed for general pseudodynamic testing. One particular subfamily seems very promising for use in general pseudodynamic testing since the stability problem for a structure does not need to be considered. This is because this subfamily is unconditionally stable for any instantaneous stiffness softening system, linear elastic system and instantaneous stiffness hardening system that might occur in the pseudodynamic testing of a real structure. In addition, it also offers good accuracy when compared to a general second-order accurate method for both linear elastic and nonlinear systems.

关键词： pseudodynamic test explicit method unconditional stability dominant mode structural dynamics instantaneous degree of nonlinearity

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Comparison of capability of time integration methods in capturing dynamic loading

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 409-423页

作者： Shuenn-yih chang Chi-Wei Hsu Department of Civil Engineering Taipei University of Technology

Numerical properties of the time integration method proposed by the first author of this paper in 2007 are the same as those of the constant average acceleration method （AAM） for linear elastic systems, except that the capability to capture dynamic loading was not explored. It was found that there were different quadrature equations to predict the next step displacement increment. A modified quadrature equation of this method was derived so that the equation to determine the next step displacement was numerically equivalent to the equation used in the constant AAM. It was verified that the original form of this method, in general, had a better capability to capture dynamic loadings than the constant AAM. This excellent property, in addition to computational efficiency, will help to make this method competitive with general secondorder accurate integration methods.

关键词： equations of motion quadrature equation constant average acceleration method integration methods

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Structure-dependent difference equations for time integration

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Earthquake Engineering and Engineering Vibration 2012年第4期11卷 485-498页

作者： Shuenn-yih chang Department of Civil Engineering Taipei University of Technology (NTUT)

A structure-dependent explicit method with enhanced stability properties is proposed in this study. In general, the method offers unconditional stability for structural systems except those with a particular instantaneous stiffness hardening behavior. In addition, it is second-order accurate and displays no overshooting in high frequency responses. Numerical experiments reveal that the proposed method saves a substantial amount of computational effort in solving inertial problems where only the low frequency responses are of interest, when compared to a general second-order accurate integration method.

关键词： time history analysis structure-dependent difference equation stability accuracy

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