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Katsumi Midorikawa - One of the best experts on this subject based on the ideXlab platform.

  • Real-Time Observation of Vibrational Wavepackets of Nitrogen Molecule Using A-Few-Pulse Attosecond Pulse Train
    Springer Series in Chemical Physics, 2018
    Co-Authors: Tomoya Okino, Yasuo Nabekawa, Katsumi Midorikawa
    Abstract:

    Observation of quantum wavepackets in Molecules is one of the vital steps in understanding chemical reactions occurring at femtosecond and attosecond timescales, because the broadband light sources inevitably coherently excite multiple quantum states. A-few-pulse attosecond pulse train generated via high-order harmonic generation in loose focusing geometry is sufficiently strong to induce multi-photon absorption processes and the pulse envelope is sufficiently short to resolve the nuclear motions. We investigated the vibrational wavepackets in a Nitrogen Molecule using a-few-pulse attosecond pulse train by measuring the pump-probe delay dependence of momentum images of fragment ions generated in singly charged manifolds via two-photon dissociative ionization processes using a velocity map imaging ion spectrometer. The time evolutions of vibrational wavepackets launched both in neutral and singly charged manifolds were projected using a frequency-resolved momentum imaging method.

  • Direct observation of an attosecond electron wave packet in a Nitrogen Molecule.
    Science advances, 2015
    Co-Authors: Tomoya Okino, A. Amani Eilanlou, Eiji J. Takahashi, Yusuke Furukawa, Yasuo Nabekawa, Kaoru Yamanouchi, Shungo Miyabe, Katsumi Midorikawa
    Abstract:

    Capturing electron motion in a Molecule is the basis of understanding or steering chemical reactions. Nonlinear Fourier transform spectroscopy using an attosecond-pump/attosecond-probe technique is used to observe an attosecond electron wave packet in a Nitrogen Molecule in real time. The 500-as electronic motion between two bound electronic states in a Nitrogen Molecule is captured by measuring the fragment ions with the same kinetic energy generated in sequential two-photon dissociative ionization processes. The temporal evolution of electronic coherence originating from various electronic states is visualized via the fragment ions appearing after irradiation of the probe pulse. This observation of an attosecond molecular electron wave packet is a critical step in understanding coupled nuclear and electron motion in polyatomic and biological Molecules to explore attochemistry.

  • Simultaneous Observation of Vibrational Wavepackets of Nitrogen Molecule in Neutral and Singly-Charged Manifolds
    Springer Proceedings in Physics, 2015
    Co-Authors: Tomoya Okino, A. Amani Eilanlou, Eiji J. Takahashi, Yusuke Furukawa, Yasuo Nabekawa, Kaoru Yamanouchi, Katsumi Midorikawa
    Abstract:

    Vibrational wavepackets of Nitrogen Molecule were created by attosecond pulse train and their time-evolutions were also probed by attosecond pulse train. Vibrational wavepackets are launched both in neutral electronic states and singly-charged electronic states of Nitrogen Molecule. The created vibrational wavepackets were excited to the dissociative states and detected as a momentum image of fragment ion using a velocity map momentum imaging ion spectrometer. The fast vibrational wavepackets \( \left( {T_{vib} = 1 5-20\,{\text{fs}}} \right) \) were ascribed to the vibrational wavepackets generated in the singly-charged electronic states. The slow vibrational wavepackets \( T_{vib} = 50-80\,{\text{fs}} \) were ascribed to the vibrational wavepackets generated in the weakly-bounded neutral electronic states. The co-existence of several vibrational wavepackets indicates the possibility to launch the electron wavepacket between these electronic states.

  • attosecond frequency resolved momentum imaging of two photon dissociative ionization dynamics of Nitrogen Molecule
    Springer Proceedings in Physics, 2015
    Co-Authors: Tomoya Okino, A. Amani Eilanlou, Eiji J. Takahashi, Yusuke Furukawa, Yasuo Nabekawa, Kaoru Yamanouchi, Katsumi Midorikawa
    Abstract:

    Two-photon dissociative ionization processes of Nitrogen Molecule are investigated with attosecond nonlinear Fourier transformation spectroscopy. Nonlinear absorption spectrum of Nitrogen Molecule are extracted by measuring interferometric autocorrelation of a-few-pulse attosecond pulse train using non-sequential two-photon processes of Nitrogen Molecule. The frequency resolved momentum images (FRMI) are reconstructed from the delay dependent momentum images of fragment ion \( {\text{N}}^{ + } \) and the resultant FRMIs show the attosecond nonlinear response of Nitrogen Molecule.

  • Attosecond Frequency Resolved Momentum Imaging of Two-photon Dissociative Ionization Dynamics of Nitrogen Molecule
    19th International Conference on Ultrafast Phenomena, 2014
    Co-Authors: Tomoya Okino, A. Amani Eilanlou, Eiji J. Takahashi, Yusuke Furukawa, Yasuo Nabekawa, Kaoru Yamanouchi, Katsumi Midorikawa
    Abstract:

    Two-photon dissociative ionization processes of Nitrogen Molecule are investigated with attosecond nonlinear Fourier transformation spectroscopy. The frequency resolved momentum images extracted from delay dependent momentum images showed attosecond nonlinear response of Nitrogen Molecule.

M Mukherjee - One of the best experts on this subject based on the ideXlab platform.

  • low energy positron Nitrogen Molecule scattering a rovibrational close coupling study
    Physical Review A, 2015
    Co-Authors: T Mukherjee, M Mukherjee
    Abstract:

    We study the positron--Nitrogen-Molecule scattering process under the rovibrational coupling method to include the effect of rotational and vibrational motion of the nuclei dynamically during the scattering process. Here we compute the angle integrated elastic and (state-to-state) rotational excitation, elastic and (state-to-state) vibrational (summed over rotational) excitation, and total (summed over rotational and vibrational) cross sections for the incident positron energy between 0.0 and 10 eV. However, in present paper we concentrate our discussion on the results in the lower-energy region, especially below 3.0 eV. To calculate the cross sections we use the model correlation polarization potential to include the distortion effect of the target electronic state in the presence of the positron. The calculated total cross sections are compared with the theoretical calculations and experimental results. The present theoretical results agree quite well with the recent theoretical and measured values. The vibrational and rotational elastic and excitation cross sections are also compared with the existing theoretical results. The state-to-state potential coupling and dynamical coupling effects on different cross sections are studied.

André Mysyrowicz - One of the best experts on this subject based on the ideXlab platform.

  • The Role of Electron Collisions in Lasing in Neutral and Singly Ionized Molecular Nitrogen
    2017
    Co-Authors: Yi Liu, Pengji Ding, Aurélien Houard, André Mysyrowicz
    Abstract:

    In this chapter, we will discuss lasing actions in the air that follow the excitation with a short intense laser pulse at 800 nm. We will successively analyze two types of laser actions. The first type is based on the optical transition between the excited triplet states of the neutral Nitrogen Molecule. Based on the study of the dependence of the lasing signal on the polarization ellipticity of the pump pulse, we unambiguously attribute gain mechanism in this scheme to the electron collisions with neutral Nitrogen Molecules that result in population inversion. Experimental results on the dynamics of emissions in the forward and backward directions with respect to the direction of the pump pulse are confirmed by numerical simulations based on the Maxwell-Bloch equations. The second type of lasing stems from the transition between the second electronically excited state and the ground state of a singly ionized Nitrogen Molecule. After reviewing current interpretations of this emission process, which remains to be a controversial issue, we will focus on our interpretation that links stimulated emission in this scheme to superradiance. We will argue that electron recollisions play an essential role in establishing the superradiant gain.

  • Recollision-Induced Superradiance of Ionized Nitrogen Molecules.
    Physical review letters, 2015
    Co-Authors: Yi Liu, Pengji Ding, Aurélien Houard, Guillaume Lambert, Vladimir Tikhonchuk, André Mysyrowicz
    Abstract:

    We propose a new mechanism to explain the origin of optical gain in the transitions between the excited and ground states of the ionized Nitrogen Molecule following irradiation of neutral Nitrogen Molecules with an intense ultrashort laser pulse. An efficient transfer of population to the excited state is achieved via field-induced multiple recollisions. We show that the proposed excitation mechanism must lead to a superradiant emission, a feature that we confirm experimentally.

  • Self-seeded lasing in ionized air pumped by 800 nm femtosecond laser pulses
    Optics Express, 2013
    Co-Authors: Yi Liu, Aurélien Houard, Yohann Brelet, Guillaume Point, André Mysyrowicz
    Abstract:

    We report on the lasing in air and pure Nitrogen gas pumped by a single 800 nm femtosecond laser pulse. Depending on gas pressure, incident laser power and beam convergence, different lasing lines are observed in the forward direction with rapid change of their relative intensities. The lines are attributed to transitions between vibrational and rotational levels of the first negative band of the singly charged Nitrogen Molecule-ion. We show that self-seeding plays an important role in the observed intensity changes.

Eizi Hirota - One of the best experts on this subject based on the ideXlab platform.

  • Fourier Transform Microwave Spectra of the Nitrogen Molecule-Ethylene Sulfide and Nitrogen Molecule-Dimethyl Sulfide Complexes.
    The journal of physical chemistry. A, 2018
    Co-Authors: Yoshiyuki Kawashima, Sakae Iwano, Eizi Hirota
    Abstract:

    We recorded the rotational spectra of N2-ethylene sulfide (ES) and N2-dimethyl sulfide (DMS) including the 15N2 and 15N14N isotopomers in the frequency range of 5-25 GHz by using a Fourier transform microwave spectrometer. The b-type transitions for the ortho and para states of 14N2-ES and 15N2-ES and c-type transitions of 14N2-DMS and 15N2-DMS were observed. The 15N14N-ES and 15N14N-DMS species were found to exist in two isomeric forms: inner (14N15N-ES and 14N15N-DMS) and outer (15N14N-ES and 15N14N-DMS). Neither the -ES nor -DMS complexes showed weak accompanying spectra, which had been observed for N2-ethylene oxide (EO). This is because the potential barriers to internal rotation of ES and DMS are higher than that of EO. The spectra were analyzed by an A-reduced asymmetric-top rotational program with less than 4 kHz standard deviation, except for the 15N14N-DMS and 14N15N-DMS complexes. Rotational, centrifugal distortion, and nuclear electric quadrupole coupling constants were determined by the spectral analysis. The V3 potential barrier to internal rotation of the two equivalent methyl groups of DMS in the ortho and para states of the 15N2-DMS complex was determined to be about 740 cm-1. We performed ab initio calculations in order to complement the information on the intracomplex motions obtained from the experimental spectra.

  • fourier transform microwave spectrum of the Nitrogen Molecule ethylene oxide complex intracomplex motions
    Journal of Physical Chemistry A, 2013
    Co-Authors: Yoshiyuki Kawashima, Eizi Hirota
    Abstract:

    The rotational spectra of the N2–ethylene oxide (EO) complex were measured in the frequency region from 4 to 27 GHz by Fourier transform microwave spectroscopy, paying particular attention to intracomplex motions. The isotopologues with enriched 15N2 or 15NN as a moiety were also investigated. We have observed spectra of a strong/weak pair for each of the ortho and para states of the 14N2–EO and 15N2–EO species, which indicated that the complex existed in four distinct states. We interpreted, on the basis of the observed relative intensities, that these states were generated primarily by the exchange of the Nitrogen atoms of the N2 moiety, followed by that of the two CH2 groups in the EO Molecule. The 15NN–EO species was found to consist of two isomers, one with the 15N in the inner expressed as N15N–EO and the other in the outer position designated as 15NN–EO, and the spectra of both isomers were accompanied by one weak set of satellites. The observed spectra were rotationally assigned by using sum rules...

Jerry Peacher - One of the best experts on this subject based on the ideXlab platform.

  • Distorted wave Born and three-body distorted wave Born approximation calculations of the fully differential cross section for electron-impact ionization of Nitrogen Molecules.
    The Journal of chemical physics, 2005
    Co-Authors: Junfang Gao, Don H. Madison, Jerry Peacher
    Abstract:

    Currently there are no reliable theoretical approaches for calculating fully differential cross sections (FDCSs) for low-energy electron-impact ionization of large Molecules. We have recently proposed the orientation-averaged molecular orbital (OAMO) for calculating cross sections averaged over molecular orientations. In this paper, we use the OAMO to calculate distorted wave Born approximation (DWBA) and molecular three-body distorted wave (M3DW) Born approximation FDCS for electron-impact ionization of the Nitrogen Molecule. Both coplanar symmetric and asymmetric FDCSs are investigated in the energy range of 35.6-400 eV. By comparing with the experimental data, we found that the M3DW is reasonably accurate in this energy range. We also found that the postcollision interaction plays a sufficiently important role and that the DWBA is not reliable.