Papers by Niels Henriksen
Coherent Control of Photofragment Distributions Using Laser Phase Modulation in the Weak-Field Limit
The journal of physical chemistry letters, Jan 5, 2015
The possibility of quantum interference control of the final state distributions of photodissocia... more The possibility of quantum interference control of the final state distributions of photodissociation fragments by means of pure phase modulation of the pump laser pulse in the weak-field regime is demonstrated theoretically for the first time. The specific application involves realistic wave packet calculations of the transient vibrational populations of the Br2(B, v(f)) fragment produced upon predissociation of the Ne-Br2(B) complex, which is excited to a superposition of resonance states using pulses with different linear chirps. Transient phase effects on the fragment populations are found to persist for long times (about 200 ps) after the pulse is over due to interference between overlapping resonances in Ne-Br2(B).
Structure and Bonding
Abstract We review the basic theoretical formulation for pulsed X-ray scattering on nonstationary... more Abstract We review the basic theoretical formulation for pulsed X-ray scattering on nonstationary molecular states. Relevant time scales are discussed for coherent as well as incoherent X-ray pulses. The general formalism is applied to a nonstationary diatomic molecule in order to highlight the relation between the signal and the time-dependent quantum distribution of internuclear positions. Finally, a few experimental results are briefly discussed.
The Journal of Physical Chemistry, 1994
The possibility of introducing an interaction picture in the semiclassical Wigner method is inves... more The possibility of introducing an interaction picture in the semiclassical Wigner method is investigated. This is done with an interaction picture description of the density operator dynamics as starting point. We show that the dynamics of the density operator dynamics as starting point. We show that the dynamics of the interaction picture Wigner function is solved by running a swarm of trajectories in the classical interaction picture introduced previously in the literature. Solving the Wigner method dynamics of collision processes in the interaction picture ensures that the calculated transition probabilities are unambiguous even when the asymptotic potentials are anharmonic. An application of the interaction picture Wigner method to a Morse oscillator interacting with a laser field is presented. The calculated transition probabilities are in good agreement with results obtained by a numerical integration of the Schrodinger equation.
Coherent Control of Photofragment Distributions Using Laser Phase Modulation in the Weak-Field Limit
The Journal of Physical Chemistry Letters, 2015
The possibility of quantum interference control of the final state distributions of photodissocia... more The possibility of quantum interference control of the final state distributions of photodissociation fragments by means of pure phase modulation of the pump laser pulse in the weak-field regime is demonstrated theoretically for the first time. The specific application involves realistic wave packet calculations of the transient vibrational populations of the Br2(B, v(f)) fragment produced upon predissociation of the Ne-Br2(B) complex, which is excited to a superposition of resonance states using pulses with different linear chirps. Transient phase effects on the fragment populations are found to persist for long times (about 200 ps) after the pulse is over due to interference between overlapping resonances in Ne-Br2(B).
Direct Dynamics Studies of a Binuclear Metal Complex in Solution: The Interplay Between Vibrational Relaxation, Coherence, and Solvent Effects
The Journal of Physical Chemistry Letters, 2014
ABSTRACT By using a newly implemented QM/MM multiscale MD method to simulate the excited state dy... more ABSTRACT By using a newly implemented QM/MM multiscale MD method to simulate the excited state dynamics of the Ir 2 (dimen) 4 2+ (dimen = 1,8-diisocyano-p-menthane) complex, we not only report on results that support the two experimentally observed coherent dynamical modes in the molecule but also reveal a third mode, not distinguishable by spectroscopic methods. We directly follow the channels of energy dissipation to the solvent and report that the main cause for coherence decay is the initial wide range of configurations in the excited state population. We observe that the solvent can actually extend the coherence lifetime by blocking channels for intramolecular vibrational energy redistribution (IVR).
Femtochemistry and Femtobiology, 2004
Ultr a fa s t n o n -F r a n c k -C o n d o n tr a n s itio n s : is it p o s s ib le ?
On the Theory of Time-Resolved X-ray Diffraction †
The Journal of Physical Chemistry B, 2008
We derive the basic theoretical formulation for X-ray diffraction with pulsed fields, using a ful... more We derive the basic theoretical formulation for X-ray diffraction with pulsed fields, using a fully quantized description of light and matter. Relevant time scales are discussed for coherent as well as incoherent X-ray pulses, and we provide expressions to be used for calculation of the experimental diffraction signal for both types of X-ray sources. We present a simple analysis of time-resolved X-ray scattering for direct bond breaking in diatomic molecules. This essentially analytical approach highlights the relation between the signal and the time-dependent quantum distribution of internuclear positions, including thermal effects.
The Journal of Physical Chemistry A, 2008
The structures of the ground and excimer states of perylene pairs are calculated [using density f... more The structures of the ground and excimer states of perylene pairs are calculated [using density functional theory (DFT) and time-dependent DFT techniques] in a free as well as a crystal environment, and their spectroscopic properties are studied for the most stable configurations. The vertical transition energies for the absorption and emission bands are obtained, and they are in good agreement with experimental data. In these calculations, up to six excited states are considered. With the calculated structures of the ground and excimer states, the scattering factors are analyzed as a function of the concentration of excimers in a crystal. The intensity of the 110, 005, and 0 10 0 reflections are found to be fairly sensitive to the presence of excimers in the crystal. The finite (nanosecond) lifetime of the excimer may make it possible to observe this state using time-resolved X-ray diffraction techniques.
Comment on “Theoretical Investigation of Perylene Dimers and Excimers and Their Signatures in X-Ray Diffraction”
The Journal of Physical Chemistry A, 2009
... Thomas S. Kuhlman , Henrik T. Lemke ¶ , Theis I. Sølling , Gustavo F. Velardez § , ... more ... Thomas S. Kuhlman , Henrik T. Lemke ¶ , Theis I. Sølling , Gustavo F. Velardez § , Niels E. Henriksen § and Klaus B. Møller* §. ... 6. All energies are relative to E 0 (∞) . 7. Hieringer, W. ; Gorling, A. Chem. Phys. Lett. ...
Approaches to Wave Packet Imaging Using Femtosecond Ionization Spectroscopy †
The Journal of Physical Chemistry A, 2004
ABSTRACT Different methods to obtain information about the probability densities of vibrational w... more ABSTRACT Different methods to obtain information about the probability densities of vibrational wave packets in diatomic molecule are compared. More explicitly, we consider pump−probe ionization processes. Time-resolved photoelectron spectra and total ion yields as well as fragment ion distributions are calculated, and these different quantities are employed to reconstruct radial densities. It is shown that pump−probe ionization experiments are well suited for the mapping of vibrational wave packets.
Suppressing the Spreading of Continuum Wave Packets via Chirped Laser Pulses †
The Journal of Physical Chemistry A, 2004
ABSTRACT We investigate the focusing, that is, the reversing of spreading of continuum wave packe... more ABSTRACT We investigate the focusing, that is, the reversing of spreading of continuum wave packets created with chirped laser pulses in the weak-field limit. Focusing can be accomplished when a negative position−momentum correlation is created in the wave packet. Specializing to constant and linear (repulsive) potentials, we show analytically that in a constant potential wave packet spreading can be compensated with positively chirped laser pulses, whereas in the linear potential negatively chirped laser pulses are required, in the short-pulse limit. The analytical results for the linear potential are supported by numerical simulations. The results are discussed in the context of a classical model for wave packet focusing.
Erratum: Theory of time-resolved inelastic x-ray diffraction [Phys. Rev. A 81, 023422 (2010)]
Physical Review A, 2010
Selective bond breakage within the HOD molecule using optimized femtosecond ultraviolet laser pulses
Physical Review A, 2008
Page 1. Selective bond breakage within the HOD molecule using optimized femtosecond ultraviolet l... more Page 1. Selective bond breakage within the HOD molecule using optimized femtosecond ultraviolet laser pulses Ashwani Kumar Tiwari, Klaus B. Møller, and Niels E. Henriksen CMM, Department of Chemistry, Building 207, Technical University of Denmark, DK-2800 Kgs. ...
Theory of time-resolved inelastic x-ray diffraction
Physical Review A, 2010
Starting from a general theory of time-resolved x-ray scattering, we derive a convenient expressi... more Starting from a general theory of time-resolved x-ray scattering, we derive a convenient expression for the diffraction signal based on a careful analysis of the relevant inelastic scattering processes. We demonstrate that the resulting inelastic limit applies to a wider variety of experimental conditions than similar, previously derived formulas, and it directly allows the application of selection rules when interpreting
Physica Scripta, 1997
We consider the time-dependent Schrodinger equation for a quadratic potential with an exponential... more We consider the time-dependent Schrodinger equation for a quadratic potential with an exponentially decaying force constant. General analytical solutions are presented and we highlight, in particular, the signatures of classical mechanics in the wave packet dynamics.
The foreland-propagating thrust architecture of the East Greenland Caledonides 72 -75 N
Journal of the Geological Society, 2004
... Headington, Oxford OX3 0BP, UK 7 7 Present address: Department of Earth Sciences, Open Univer... more ... Headington, Oxford OX3 0BP, UK 7 7 Present address: Department of Earth Sciences, Open University, Walton Hall, Milton Keynes MK7 ... to Lower Palaeozoic succession, structurally overlain by two major Caledonian thrust sheets (Niggli Spids and Hagar Bjerg Thrust Sheets). ...
The first absorption band for H2O: Interpretation of the absorption spectrum using time dependent pictures
The Journal of Chemical Physics, 1988
We examine the relation between photodissociation dynamics and the form of the total absorption s... more We examine the relation between photodissociation dynamics and the form of the total absorption spectrum for H2O in the first absorption band. Application of an exact time dependent formalism gives a direct and intuitive relation between molecular motion and spectral features. We show that the series of weak structures on top of the broad continuum is due to symmetric stretch motion in the excited state. The spacing between the structures is, essentially, given by the frequency associated with this motion. In addition, we present some excited state eigenfunctions, which provide a direct connection between the structured spectrum, the final product distributions, and the dynamics.
Test of the Wigner method for the photodissociation of symmetric triatomic molecules
The Journal of Chemical Physics, 1987
ABSTRACT
The Journal of Chemical Physics, 1992
A scheme for controlling the outcome of a photodissociation process is studied. It involves two l... more A scheme for controlling the outcome of a photodissociation process is studied. It involves two lasers-one intense laser in the infrared region which is supposed to excite a particular bond in the electronic ground state, and a second short laser pulse in the ultraviolet region which, at the right moment, excites the molecule to a dissociative electronic state. We consider the HOD molecule which is ideal due to the local mode structure of the vibrational states. It is shown that selective and localized bond stretching can be created in simple laser fields. When such a nonstationary vibrating HOD molecule is photodissociated with a short laser pulse ( -5 fs) complete selectivity between the channels H + OD and D + OH is observed over the entire absorption band covering these channels.
Quantum dynamics via a time propagator in Wigner’s phase space
The Journal of Chemical Physics, 1995
We derive an expression for a short-time phase space propagator. We use it in a new propagation s... more We derive an expression for a short-time phase space propagator. We use it in a new propagation scheme and demonstrate that it works for a Morse potential. The propagation scheme is used to propagate classical distributions which do not obey the Heisenberg uncertainty principle. It is shown that the simple classical deterministic motion breaks down surprisingly fast in an anharmonic potential. Finally, we discuss the possibility of using the scheme as a useful approach to quantum dynamics in many dimensions. To that end we present a Monte Carlo integration scheme using the norm of the propagator as a part of the sampling function.
Uploads
Papers by Niels Henriksen