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We studied the behavior of the continuous rolling motion (CRM) of a disk placed on a vibrating plate observed in the experiment using numerical simulations. Numerical simulations show that a rolling disk on a vibrating plate abruptly stops in case of pure rolling without slipping, whereas CRM occurs in the case of slipping. CRM occurs in two frequency bands separated by a gap. We use numerical simulations to determine the gap and the frequency domains for different values of the coefficient of sliding friction. The characteristics of rolling motion depend on the coefficient of slip friction and frequency of vibration. [ABSTRACT FROM AUTHOR]

In an attempt to expand the utility of the model Hamiltonian technique developed by Köppel, Domcke, and Cederbaum (KDC) [Adv. Chem. Phys. 57, 59 (1984)], an ansatz for quasidiabatic wave functions is introduced in the framework of equation-of-motion coupled-cluster (EOM-CC) theory. Based on the ansatz, the theory for the analytic first derivative of the off-diagonal element of the quasidiabatic potential matrix is developed by extending the theory for the analytic gradient of the EOM-CC energy. This analytic derivative is implemented for EOM-CCSD (singles and doubles approximation) calculations of radicals subject to pseudo-Jahn–Teller and Jahn–Teller interactions. Its applicability in construction of the KDC quasidiabatic model potential is discussed. [ABSTRACT FROM AUTHOR]

The 351.1 nm photoelectron spectrum of the cyclopentadienide ion has been measured, which reveals the vibronic structure of the X 2E1″ state of the cyclopentadienyl radical. Equation-of-motion ionization potential coupled-cluster (EOMIP-CCSD) calculations have been performed to construct a diabatic model potential of the X 2E1″ state, which takes into account linear Jahn–Teller effects along the e2′ normal coordinates as well as bilinear Jahn–Teller effects along the e2′ and ring-breathing a1′ coordinates. A simulation based on this ab initio model potential reproduces the spectrum very well, identifying the vibronic levels with linear Jahn–Teller angular momentum quantum numbers of ±1/2. The angular distributions of the photoelectrons for these vibronic levels are highly anisotropic with the photon energies used in the measurements. A few additional weak photoelectron peaks are observed when photoelectrons ejected parallel to the laser polarization are examined. These peaks correspond to the vibronic levels for out-of-plane modes in the ground X 2E1″ state, which arise due to several pseudo-Jahn–Teller interactions with excited states of the radical and quadratic Jahn–Teller interaction in the X 2E1″ state. A variant of the first derivative of the energy for the EOMIP-CCSD method has been utilized to evaluate the strength of these nonadiabatic couplings, which have subsequently been employed to construct the model potential of the X 2E1″ state with respect to the out-of-plane normal coordinates. Simulations based on the model potential successfully reproduce the weak features that become conspicuous in the 0° spectrum. The present study of the photoelectron spectrum complements a previous dispersed fluorescence spectroscopic study by Miller and co-workers [J. Chem. Phys. 114, 4855 (2001); 114, 4869 (2001)] to provide a detailed account of the vibronic structure of X 2E1″ cyclopentadienyl. The electron affinity of the cyclopentadienyl radical is determined to be 1.808±0.006 eV. This electron affinity and the gas-phase acidity of cyclopentadiene have been combined in a negative ion thermochemical cycle to determine the C–H bond dissociation energy of cyclopentadiene; D0(C5H6,C–H)=81.5±1.3 kcal mol-1. The standard enthalpy of formation of the cyclopentadienyl radical has been determined to be ΔfH298(C5H5)=63.2±1.4 kcal mol-1. [ABSTRACT FROM AUTHOR]

The 351.1 nm photoelectron spectrum of the 1-pyrazolide-d3 anion has been measured. The photoelectron angular distributions indicate the presence of nearly degenerate electronic states of the 1-pyrazolyl-d3 radical. Equation-of-motion ionization potential coupled-cluster singles and doubles (EOMIP-CCSD) calculations have been performed to study the low-lying electronic states. The calculations strongly suggest that three electronic states, energetically close to each other, are accessed in the photodetachment process. Strong interactions of the pseudo-Jahn-Teller type in each pair of the three states are evident in the calculations for the radical at the anion geometry. Model diabatic potentials of the three states have been constructed around the anion geometry in terms of the anion reduced normal coordinates up to the second order. An analytic method to parametrize the quadratic vibronic coupling (QVC) model potentials has been introduced. Parameters of the QVC model potentials have been determined from the EOMIP-CCSD and CCSD(T) calculations. Simulations of the 1-pyrazolide-d3 spectrum have been performed with the model Hamiltonian, treating all vibronic interactions amongst the three states simultaneously. The simulation reproduces the fine structure of the observed spectrum very well, revealing complicated nonadiabatic effects in the low-lying states of the radical. The ground state of the 1-pyrazolyl-d3 radical is 2A2 and the electron affinity is 2.935±0.006 eV. The first excited state is 2B1 with a term energy of 32±1 meV. While the high-symmetry (C2v) stationary points of the X 2A2 and à 2B1 states are minima, that of the state is a saddle point as a result of the pseudo-Jahn-Teller interactions with the other two states. The topology of the adiabatic potential energy surfaces is discussed. [ABSTRACT FROM AUTHOR]

Recently, it has been proposed that various kinds of time operations can be performed using an excitable field, mainly based on computer simulation. In this study, we performed experiments toward the realization of a time operation, such as time-difference detection. We used the photosensitive Belousov–Zhabotinsky reaction as a spatially distributed excitable field. We found that a single geometrical circuit can perform different operations with changes in the intensity of light illumination. The experimental results are discussed in relation to the idea of a non-Neumann-type computational device. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The electronic and vibrational absorption spectra of the radical anion and cation of p-benzoquinone (PBQ) in an Ar matrix between 500 and 40 000 cm−1 are presented and discussed in detail. Of particular interest is the radical cation, which shows very unusual spectroscopic features that can be understood in terms of vibronic coupling between the ground and a very low-lying excited state. The infrared spectrum of PBQṖ+ exhibits a very conspicuous and complicated pattern of features above 1900 cm−1 that is due to this electronic transition, and offers an unusually vivid demonstration of the effects of vibronic coupling in what would usually be a relatively simple region of the electromagnetic spectrum associated only with vibrational transitions. As expected, the intensities of most of the IR transitions leading to levels that couple the ground to the very low-lying first excited state of PBQṖ+ increase by large factors upon ionization, due to “intensity borrowing” from the D0→ D1 electronic transition. A notable exception is the antisymmetric C=O stretching vibration, which contributes significantly to the vibronic coupling, but has nevertheless quite small intensity in the cation spectrum. This surprising feature is rationalized on the basis of a simple perturbation analysis. [ABSTRACT FROM AUTHOR]

The performance of different choices of parametrization for the quasidiabatic Hamiltonian approach of Köppel et al. (Adv Chem Phys 57:59, ) is studied for the $${\tilde X}^2A_1$$ and $${\tilde A}^2B_2$$ states of the formyloxyl radical, $$\hbox{HCO}_2$$. Two basic classes of parametrization are analyzed. In the first (vertical), the model Hamiltonian is constructed in such a way that it reproduces an ab initio surface near the geometry of the absorbing state in a spectroscopic transition; the second scheme (adiabatic) is designed to provide a faithful representation of the ab initio surface near the final state structures. The latter is better suited to treat energy level spacings, especially at relatively low energies, while the former may offer advantages in some cases where it may provide a more balanced description of the final states and/or features such as seams of conical intersections. For $$\hbox{HCO}_2$$, the most interesting and prominent feature of the vibronic coupling scheme is a strong coordinate dependence of the coupling between the two electronic states. This effect renders effectively useless parametrization approaches in which the linear coupling strength is assumed constant. Moreover, through selective softening of the A state potential and corresponding reduction in its zero-point energy, this seemingly arcane property of the vibronic coupling in $$\hbox{HCO}_2$$ is principally responsible for the ground state of this molecule being A instead of B, as the adiabatic potential energy surface minimum of the latter is some 500 $$\hbox{cm}^{-1}$$ lower. [ABSTRACT FROM AUTHOR]

A joint experimental-theoretical study has been carried out on electronic states of propadienylidene (H2CCC), using results from negative-ion photoelectron spectroscopy. In addition to the previously characterized X1A1 electronic state, spectroscopic features are observed that belong to five additional states: the low-lying ã3B1 and b3A2 states, as well as two excited singlets, Ã1A2 and B1B1, and a higher-lying triplet, c3A1. Term energies (T0, in cm-1) for the excited states obtained from the data are: 10 354±11 (ã3B1); 11 950±30 (b3A2); 20 943±11 (c3A1); and 13 677±11 (Ã1A2). Strong vibronic coupling affects the Ã1A2 and B1B1 states as well as ã3B1 and b3A2 and has profound effects on the spectrum. As a result, only a weak, broadened band is observed in the energy region where the origin of the B1B1 state is expected. The assignments here are supported by high-level coupled-cluster calculations and spectral simulations based on a vibronic coupling Hamiltonian. A result of astrophysical interest is that the present study supports the idea that a broad absorption band found at 5450 Å by cavity ringdown spectroscopy (and coincident with a diffuse interstellar band) is carried by the B1B1 state of H2CCC. [ABSTRACT FROM AUTHOR]