© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Coherent control of photoelectron angular distributions in nitric oxide

Rana Shehadeh

Published Jan 1, 1995• 0 citations

Abstract

In this study, we extended the coherent control theory proposed by Brumer and Shapiro to bound-continuum transition in a molecular system where control of the ejection direction of photoelectrons in the ionization of nitric oxide was achieved. Nitric oxide was prepared in its first excited Rydberg state and was then ionized simultaneously by two different paths: a one-photon and a two-photon process. The fundamental and second harmonic frequencies of a dye laser were used for the two different ionization processes. Interference due to the two paths was detected by measuring the photoelectrons ejected in a defined solid angle. Changing the relative phase between the two paths resulted in a destructive or constructive interference leading to a decrease or increase of the measured signal, respectively. This study showed that interference experiments are very sensitive, not only to lasers' properties and the optical components, but also to the properties of the molecular system. Laser properties, such as, spatial and temporal mode qualities, power fluctuations and timing, influenced the relative strength of the signals of the two ionization paths. Optical component properties, such as, surface parallelism and quality, affected laser divergence, and therefore, considerably reduced the depth of modulation. As for the molecular system, in a resonance two-photon excitation, appropriate resonance states must be chosen to ensure that the two processes produce electron waves of opposite parities which can interfere constructively to produce an enhancement of electron ejection in a certain direction. Due to the non-ideal properties of the lasers used, it is best to use a non-resonant two-photon ionization as one of the interfering paths. Resonant two-photon ionization, combined with the multi-mode laser greatly reduced the depth of the modulation.

Related papers

Coherent control of optical processes through interfering interactions

Yi-Yian Yin, Rana Shehadeh, Edward R. Grant +1 more

Prospects for the coherent control of optically-induced processes have attracted a great deal of interest of late. In this talk we will discuss our recent demonstration of the first example of two-pathway coherent control on a bound-free transition in a molecular system. In this demonstration, we controlled the asymmetry of the angular distribution of photoelectrons produced by photoionization of NO. Preparation of the NO in its A{sup 2}{Sigma}, state allowed isolation of a single rotational state, which was subsequently ionized via interfering one- and two-photon interactions. We discuss the role of intermediate-state resonances and laser mode quality on two-pathway control processes.

•Dec 1, 1995•0 citations

Temporal phase control of bound-bound and bound-free two-photon transitions in NO with two time-delayed cross-polarized pulses

Claude Doulé, E. Hertz, Lotfi Berguiga +3 more

Temporal phase control over the multi-photoionization of NO is investigated experimentally. The coherent excitation of the molecular system is achieved by a sequence of two phase-related non-Fourier-transform-limited laser pulses delivered by a nanosecond dye laser. The phase-locked pulses are produced by making use of an actively stabilized interferometer with a tunable path-length difference. As the coherence time of the laser is comparable with the inhomogenous dephasing time of the medium, the measurements are performed with temporally overlapped pulses. In order to avoid the modulation of the ionic signal coming from optical interference, the linear polarizations of the two pulses are crossed. The quantum modulation of the signal versus the time delay between the two pulses is observed for the three following distinct processes: (a) two-photon resonant four-photon ionization of the ground vibronic state; (b) two-photon absorption of the A-X transition followed by ionization; and (c) two-photon ionization of the electronically excited state A. As a result, temporal phase control over bound-bound and bound-free transitions is demonstrated. The efficiency of the control process is shown to be limited by the presence of uncoupled excitation channels inherent to the method employed. The advantage in using a sequence of cross-polarized pulses for the controlling processes is discussed.

Journal of Physics B Atomic Molecular and Optical Physics•Mar 14, 2001•5 citations

Coherent control of atomic photoionization

Stefano Cavalieri, R. Eramo, Luca Fini +1 more

Coherent control provides a quantum interference based method for controlling atomic and molecular dynamics. We report two experimental observations of different ways to achieve such a control in atomic photoionization continuum. One is the photoionization of sodium atoms, initially prepared in the 3P1/2 excited state, by a non resonant three-photon interaction with 1064-nm laser light and by a one-photon interaction with the third-harmonic field, at 355 nm. Interference between the two transition paths allows the control of the total ionization rate by varying the relative phase of the laser fields. The second experiment is the observation of the modification of the ionization continua of xenon through laser induced continuum structure (LICS). The multiphoton radiative decay of the xenon ground state into the two electronic continua, that correspond to the two fine structure levels of the ground state of the xenon ion, is varied by electromagnetically embedding a bound state of the atom into the two continua. Both experiments are performed on an atomic beam apparatus which uses a time-of-flight spectrometer for energy analyzing the emitted photoelectrons.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Oct 21, 1998•0 citations

One- and two-photon phase-sensitive coherent control of total ionization yields in the presence of static electric fields

Agisilaos Bolovinos, S. Cohen, Ioannis Liontos

We experimentally demonstrate one- and two-photon phase sensitive coherent control over the excitation and ionization of Rydberg states of Sr atom in the presence of a static homogeneous electric field. Without the field this excitation scheme can only be employed for the manipulation of angular distributions of photoelectrons and molecular photofragmentation products. Total atomic excitation-ionization yields cannot be modulated because the final states excited by each pathway are orthogonal to each other. When, however, a static electric field is applied, $s$, $p$ and $d$ character is admixed into the final Rydberg state, which has no definite parity anymore. Hence, the excitation of the target Stark state from the ground state is possible with either two (fundamental laser frequency) photons or one (second harmonic frequency) photon and its population and further ionization can be controlled by varying the relative phase between the two radiation fields. The concept is successfully tested below as well as above the classical saddle point and with either mutually crossed or parallel linear laser beam polarizations (while the second harmonic beam polarization vector is always parallel to the static field direction). We examine the behavior of the obtained photoionization signal modulation depth $V$ as a function of the static field strength $F$ for otherwise identical experimental conditions. The $V(F)$ curve exhibits a maximum (typically $\ensuremath{\sim}65%--85%$) at a field strength value that is dictated by the interplay between the employed laser power densities, one- and two-photon transition dipole moments, and relative amounts of field-dependent $s$, $p$ and $d$ character. It is therefore shown that the static field strength may serve as an additional, experimentally adjustable, control parameter in a fashion complementary to both the intensities and relative phase of the two light beams.

Physical Review A•Feb 14, 2008•11 citations

Observation of laser-induced continuum structure in the NO molecule

O. Faucher, E. Hertz, B. Lavorel +4 more

We present experimental results on the modification of a molecular ionization continuum through a laser-induced continuum structure. The effect is demonstrated in nitric oxide where the resonant 2 + 1 multiphoton-ionization process of the X 2 3/2 electronic ground state is modified by dressing the continuum with the electromagnetically embedded M 2 + Rydberg state. Through selection of a two-photon rovibronic transition via the D electronic state, a single rotational ground state level is excited to the continuum with one laser field. By adding an extra dressing field, a coupling is then established between this three-photon excited ground state level and one of the M state rotational levels. The modification due to the dressed continuum results in a modification of the ground state level ionization signal in one of the decay channels where an asymmetric line-shape resonance is electromagnetically induced. Limiting effects due to ac-Stark shifts are discussed.

Journal of Physics B Atomic Molecular and Optical Physics•Sep 13, 1999•31 citations

Quantum coherent control of the photoelectron angular distribution in bichromatic-field ionization of atomic neon

Грызлова Елена Владимировна, Alexei N. Grum-Grzhimailo, Ekaterina I. Staroselskaya +2 more

We investigate the coherent control of the photoelectron angular distribution in bichromatic atomic ionization. Neon is selected as target since it is one of the most popular systems in current gas-phase experiments with free-electron lasers (FELSs). In particular, we tackle practical questions, such as the role of the fine-structure splitting, the pulse length, and the intensity. Time-dependent and stationary perturbation theory are employed, and we also solve the time-dependent Schr\"odinger equation in a single-active electron model. We consider neon ionized by a FEL pulse whose fundamental frequency is in resonance with either $2p\text{\ensuremath{-}}3s$ or $2p\text{\ensuremath{-}}4s$ excitation. The contribution of the nonresonant two-photon process and its potential constructive or destructive role for quantum coherent control is investigated.

arXiv:1712.00842•Physical Review A•Jan 26, 2018•29 citations

In this study, we extended the coherent control theory proposed by Brumer and Shapiro to bound-continuum transition in a molecular system where control of the ejection direction of photoelectrons in the ionization of nitric oxide was achieved. Nitric oxide was prepared in its first excited Rydberg state and was then ionized simultaneously by two different paths: a one-photon and a two-photon process. The fundamental and second harmonic frequencies of a dye laser were used for the two different ionization processes. Interference due to the two paths was detected by measuring the photoelectrons ejected in a defined solid angle. Changing the relative phase between the two paths resulted in a destructive or constructive interference leading to a decrease or increase of the measured signal, respectively. This study showed that interference experiments are very sensitive, not only to lasers' properties and the optical components, but also to the properties of the molecular system. Laser properties, such as, spatial and temporal mode qualities, power fluctuations and timing, influenced the relative strength of the signals of the two ionization paths. Optical component properties, such as, surface parallelism and quality, affected laser divergence, and therefore, considerably reduced the depth of modulation. As for the molecular system, in a resonance two-photon excitation, appropriate resonance states must be chosen to ensure that the two processes produce electron waves of opposite parities which can interfere constructively to produce an enhancement of electron ejection in a certain direction. Due to the non-ideal properties of the lasers used, it is best to use a non-resonant two-photon ionization as one of the interfering paths. Resonant two-photon ionization, combined with the multi-mode laser greatly reduced the depth of the modulation.

Prospects for the coherent control of optically-induced processes have attracted a great deal of interest of late. In this talk we will discuss our recent demonstration of the first example of two-pathway coherent control on a bound-free transition in a molecular system. In this demonstration, we controlled the asymmetry of the angular distribution of photoelectrons produced by photoionization of NO. Preparation of the NO in its A{sup 2}{Sigma}, state allowed isolation of a single rotational state, which was subsequently ionized via interfering one- and two-photon interactions. We discuss the role of intermediate-state resonances and laser mode quality on two-pathway control processes.

Temporal phase control over the multi-photoionization of NO is investigated experimentally. The coherent excitation of the molecular system is achieved by a sequence of two phase-related non-Fourier-transform-limited laser pulses delivered by a nanosecond dye laser. The phase-locked pulses are produced by making use of an actively stabilized interferometer with a tunable path-length difference. As the coherence time of the laser is comparable with the inhomogenous dephasing time of the medium, the measurements are performed with temporally overlapped pulses. In order to avoid the modulation of the ionic signal coming from optical interference, the linear polarizations of the two pulses are crossed. The quantum modulation of the signal versus the time delay between the two pulses is observed for the three following distinct processes: (a) two-photon resonant four-photon ionization of the ground vibronic state; (b) two-photon absorption of the A-X transition followed by ionization; and (c) two-photon ionization of the electronically excited state A. As a result, temporal phase control over bound-bound and bound-free transitions is demonstrated. The efficiency of the control process is shown to be limited by the presence of uncoupled excitation channels inherent to the method employed. The advantage in using a sequence of cross-polarized pulses for the controlling processes is discussed.

Coherent control provides a quantum interference based method for controlling atomic and molecular dynamics. We report two experimental observations of different ways to achieve such a control in atomic photoionization continuum. One is the photoionization of sodium atoms, initially prepared in the 3P1/2 excited state, by a non resonant three-photon interaction with 1064-nm laser light and by a one-photon interaction with the third-harmonic field, at 355 nm. Interference between the two transition paths allows the control of the total ionization rate by varying the relative phase of the laser fields. The second experiment is the observation of the modification of the ionization continua of xenon through laser induced continuum structure (LICS). The multiphoton radiative decay of the xenon ground state into the two electronic continua, that correspond to the two fine structure levels of the ground state of the xenon ion, is varied by electromagnetically embedding a bound state of the atom into the two continua. Both experiments are performed on an atomic beam apparatus which uses a time-of-flight spectrometer for energy analyzing the emitted photoelectrons.

We experimentally demonstrate one- and two-photon phase sensitive coherent control over the excitation and ionization of Rydberg states of Sr atom in the presence of a static homogeneous electric field. Without the field this excitation scheme can only be employed for the manipulation of angular distributions of photoelectrons and molecular photofragmentation products. Total atomic excitation-ionization yields cannot be modulated because the final states excited by each pathway are orthogonal to each other. When, however, a static electric field is applied,

s

,

p

and

d

character is admixed into the final Rydberg state, which has no definite parity anymore. Hence, the excitation of the target Stark state from the ground state is possible with either two (fundamental laser frequency) photons or one (second harmonic frequency) photon and its population and further ionization can be controlled by varying the relative phase between the two radiation fields. The concept is successfully tested below as well as above the classical saddle point and with either mutually crossed or parallel linear laser beam polarizations (while the second harmonic beam polarization vector is always parallel to the static field direction). We examine the behavior of the obtained photoionization signal modulation depth

V

as a function of the static field strength

F

for otherwise identical experimental conditions. The

V(F)

curve exhibits a maximum (typically $\ensuremath{\sim}65%--85%$) at a field strength value that is dictated by the interplay between the employed laser power densities, one- and two-photon transition dipole moments, and relative amounts of field-dependent

s

,

p

and

d

character. It is therefore shown that the static field strength may serve as an additional, experimentally adjustable, control parameter in a fashion complementary to both the intensities and relative phase of the two light beams.

We present experimental results on the modification of a molecular ionization continuum through a laser-induced continuum structure. The effect is demonstrated in nitric oxide where the resonant 2 + 1 multiphoton-ionization process of the X 2 3/2 electronic ground state is modified by dressing the continuum with the electromagnetically embedded M 2 + Rydberg state. Through selection of a two-photon rovibronic transition via the D electronic state, a single rotational ground state level is excited to the continuum with one laser field. By adding an extra dressing field, a coupling is then established between this three-photon excited ground state level and one of the M state rotational levels. The modification due to the dressed continuum results in a modification of the ground state level ionization signal in one of the decay channels where an asymmetric line-shape resonance is electromagnetically induced. Limiting effects due to ac-Stark shifts are discussed.

We investigate the coherent control of the photoelectron angular distribution in bichromatic atomic ionization. Neon is selected as target since it is one of the most popular systems in current gas-phase experiments with free-electron lasers (FELSs). In particular, we tackle practical questions, such as the role of the fine-structure splitting, the pulse length, and the intensity. Time-dependent and stationary perturbation theory are employed, and we also solve the time-dependent Schr\"odinger equation in a single-active electron model. We consider neon ionized by a FEL pulse whose fundamental frequency is in resonance with either $2p\text{\ensuremath{-}}3s$ or $2p\text{\ensuremath{-}}4s$ excitation. The contribution of the nonresonant two-photon process and its potential constructive or destructive role for quantum coherent control is investigated.