| 1. |
- Burmeister, F., et al.
(författare)
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A study of the inner-valence ionization region in HCl and DCl
- 2004
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:6, s. 1173-1183
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Tidskriftsartikel (refereegranskat)abstract
- An in-depth photoionization study of the inner-valence electrons in HCl and DCl has been performed using synchrotron radiation. A series of photoelectron spectra of HCl were obtained at a resolution of 23 meV over the binding energy range 25-30.5 eV at various excitation energies and at two different electron collection angles relative to the plane of polarization of the undulator radiation. In addition, photoelectron spectra of DCl were recorded at two different excitation energies. These spectra were compared directly with the threshold photoelectron spectra of HCl and DCl that were recorded previously under similar resolution conditions (similar to30 meV). This comparative study reveals new information on the nature of the numerous band systems observed in this binding energy region. In addition, we present the experimental confirmation of the theoretical prediction given by Andersson et al (2001 Phys. Rev. A 65 012705) that a vibrational progression showing interference structure would appear in the main inner-valence ionization band in the photoelectron spectrum of DCl at a resolution of 10 meV.
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| 2. |
- Andersson, L. Mauritz, et al.
(författare)
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Nonadiabatic effects in the photoelectron spectra of HCl and DCl. II. Theory
- 2002
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 65:1
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Tidskriftsartikel (refereegranskat)abstract
- The vibrationally resolved photoelectron spectra of HCl and DCl in the 25-28 eV region were computed using a time-dependent approach for the nuclear dynamics. The spectral features cannot be understood without including a nonadiabatic coupling between the dissociative 3 (2)Sigma(+) state and the bound 4 (2)Sigma(+) state in the adiabatic picture. Alternatively, in the diabatic picture a dissociative two-hole-one-particle state interacts with a bound one-hole state. The molecular system is of intermediate coupling strength, i.e., it cannot be described by a single potential-energy curve. The interaction between a bound and a dissociative state leads to Fano resonances superimposed on a broad back-round, as observed in the experimental spectra [Burmeister et al., Phys. Rev. A 65, 012704 (2001)]. From modified potential-energy curves, all features of the experimental spectra, including Fano resonance parameters and lifetimes, were reproduced. From the simulations we observe that two additional peaks in the experimental DCl spectra should appear if the resolution were to be enhanced to around 10 meV.
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| 3. |
- Andersson, L. Mauritz, et al.
(författare)
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Properties of a discretized coherent state representation and the relation to Gabor analysis
- 2002
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Ingår i: Journal of Physics A. - : IOP Publishing. - 0305-4470 .- 1361-6447. ; 35:36, s. 7787-7801
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Tidskriftsartikel (refereegranskat)abstract
- Properties of a discretized coherent state representation (DCSR) and its connection to Gabor frame analysis are discussed. The DCSR approach was recently shown (Andersson L M 2001 J. Chem. Phys. 115 1158) to yield a practical computational scheme for quantum dynamics, and an iterative scheme for finding the identity operator was proposed. In the present work, we suggest a proof of fast convergence of the iterative scheme for computing the canonical dual to any given countable frame in a Hilbert space. The method of frames is concerned with the use of a non-orthogonal, over-complete set of functions for expansion of an arbitrary function. We also introduce the concept of 'representations of the identity operator' and show how to expand arbitrary vectors using the frame elements, without explicit diagonalization to an orthonormal basis. Numerical examples that illustrate the method are shown.
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| 4. |
- Karlsson, H O, et al.
(författare)
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Correlation functions and thermal rate constants
- 2001
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 105:12, s. 2599-2603
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Tidskriftsartikel (refereegranskat)abstract
- Thermal rate constants k(T) and cumulative reaction probabilities N(E) can be computed as a sum of correlation functions C-nm = <(n)/f((H) over tilde/phi (m)). In this paper we discuss the use of two different Krylov subspace methods to compute these correlation functions for large systems. The first approach is based on the Lanczos algorithm to transform the Hamiltonian to tridiagonal form. As shown by Mandelshtam (J. Chem, Phys. 1998, 108, 9999) and Chen and Guo (J, Chem. Phys. 1999, 111, 9944), ail correlation functions can be computed from a single recursion. The second approach treats a number of linear systems of equations using a Krylov subspace solver. Here the quasiminimal residual (QMR) method was used. For the first approach, we found that we needed the same number of Lanczos recursions as the size of the matrix. If Ilo re-orthogonalization is used, the number of recursions grows further. The linear solver approach, on the other hand, converges fast for each linear system, but many systems must be solved.
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| 5. |
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| 6. |
- Andersson, LM, et al.
(författare)
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Vibrational wave packet dynamics in NaK : The A (1)Sigma(+) state
- 1999
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 241:1, s. 43-54
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Tidskriftsartikel (refereegranskat)abstract
- A combined experimental and theoretical study of the vibrational wave packet dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. The experiment utilises a 790 nm one-colour femtosecond pump-probe scheme with detection of a previously nor reported dissociation pathway of the 3 (1)Pi(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a molecular cascading process via the 4 (1)Sigma(+) state, which crosses several states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum mechanical calculations are used for studying the dynamics in detail. Simulations are performed both for 790 nm and for 766 nm, to relate also to earlier studies. The previous interpretations of the probe processes are revised. Inclusion of vibrational and rotational temperature effects are shown to be crucial for explaining the shape of the signal and the vibrational period, and leads to excellent agreement with the experiments.
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| 7. |
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| 8. |
- Carlsen, H, et al.
(författare)
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Dynamics of particles for circular Rydberg states
- 1999
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Ingår i: PHYSICAL REVIEW A. - 1050-2947. ; 59:2, s. 1063-1069
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The dynamics of circular Rydberg wave packets for the hydrogen atom with particular emphasis on fractional and full revivals previously studied by Gaeta and Stroud [Phys. Rev. A 42, 6308 (1990)], is developed within the de Broglie-Bohm pilot-wave theory.
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| 9. |
- Goscinski, O
(författare)
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Calculation of dispersion energy shifts in molecular electronic spectra using sum rules
- 2001
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Ingår i: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY. - : JOHN WILEY & SONS INC. - 0020-7608. ; 81:3, s. 202-205
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Tidskriftsartikel (refereegranskat)abstract
- The use of factorization formulas due to Casimir and Polder gives exact expressions for van der Waals energies in terms of the dynamic properties of the subsystems. It is natural to approximate the appearing polarizabilities in terms of rational fractions
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| 10. |
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