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Direct observation of an attosecond electron wave packet in a nitrogen molecule.

Okino T, Furukawa Y, Nabekawa Y, Miyabe S, Amani Eilanlou A, Takahashi EJ, Yamanouchi K, Midorikawa K - Sci Adv (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Attosecond Science Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.

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.

No MeSH data available.


Related in: MedlinePlus

Scheme for observing EWP in a nitrogen molecule.(A) A-few-pulse APT excites electronic states (shaded light green) to prepare an EWP at the time tpump. The a-few-pulse APT probe with time delay Δt excites relevant electronic states to the dissociative electronic states in N2+ (shaded light yellow) to trigger the fragmentation (N+ + N) at the time tprobe. Momentum images of fragment N+ were recorded by scanning the delay Δt. The bottom image shows the numerically simulated nuclear wave packets related to the EWP obtained by considering the superposition of five electronic states . (B) Potential energy curves of electronic states relevant to the EWP formation and the harmonic distribution constituting the APT. L1, L2, and L3 are dissociation limits. arb.u., arbitrary unit.
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Figure 1: Scheme for observing EWP in a nitrogen molecule.(A) A-few-pulse APT excites electronic states (shaded light green) to prepare an EWP at the time tpump. The a-few-pulse APT probe with time delay Δt excites relevant electronic states to the dissociative electronic states in N2+ (shaded light yellow) to trigger the fragmentation (N+ + N) at the time tprobe. Momentum images of fragment N+ were recorded by scanning the delay Δt. The bottom image shows the numerically simulated nuclear wave packets related to the EWP obtained by considering the superposition of five electronic states . (B) Potential energy curves of electronic states relevant to the EWP formation and the harmonic distribution constituting the APT. L1, L2, and L3 are dissociation limits. arb.u., arbitrary unit.

Mentions: In contrast, here we present the direct observation of temporal evolution of the EWP in a nitrogen molecule by the attosecond-pump/attosecond-probe method using nonlinear Fourier transform spectroscopy (NFTS) (27). The scheme for observing the EWP in N2 is shown schematically in Fig. 1A. The potential energy curves of electronic states relevant to the EWP formation are shown in Fig. 1B with the harmonic distribution of a-few-pulse attosecond pulse train (APT) composed of a few attosecond pulses in the envelope. The pump pulse creates a coherent EWP among the bound electronic states in N2 and N2+. Note that the latter involves the ejection of a photoelectron. The probe pulse excites all electronic states involved in the EWP to respective dissociative electronic states in N2+ and triggers fragmentation to generate the N+ ion. The pump-probe delay-dependent kinetic energy (KE) distribution of N+ exhibits at least four characteristic oscillations from 500 as to 3.5 fs ascribed to the electronic motion or charge oscillation between two electronic states.


Direct observation of an attosecond electron wave packet in a nitrogen molecule.

Okino T, Furukawa Y, Nabekawa Y, Miyabe S, Amani Eilanlou A, Takahashi EJ, Yamanouchi K, Midorikawa K - Sci Adv (2015)

Scheme for observing EWP in a nitrogen molecule.(A) A-few-pulse APT excites electronic states (shaded light green) to prepare an EWP at the time tpump. The a-few-pulse APT probe with time delay Δt excites relevant electronic states to the dissociative electronic states in N2+ (shaded light yellow) to trigger the fragmentation (N+ + N) at the time tprobe. Momentum images of fragment N+ were recorded by scanning the delay Δt. The bottom image shows the numerically simulated nuclear wave packets related to the EWP obtained by considering the superposition of five electronic states . (B) Potential energy curves of electronic states relevant to the EWP formation and the harmonic distribution constituting the APT. L1, L2, and L3 are dissociation limits. arb.u., arbitrary unit.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643781&req=5

Figure 1: Scheme for observing EWP in a nitrogen molecule.(A) A-few-pulse APT excites electronic states (shaded light green) to prepare an EWP at the time tpump. The a-few-pulse APT probe with time delay Δt excites relevant electronic states to the dissociative electronic states in N2+ (shaded light yellow) to trigger the fragmentation (N+ + N) at the time tprobe. Momentum images of fragment N+ were recorded by scanning the delay Δt. The bottom image shows the numerically simulated nuclear wave packets related to the EWP obtained by considering the superposition of five electronic states . (B) Potential energy curves of electronic states relevant to the EWP formation and the harmonic distribution constituting the APT. L1, L2, and L3 are dissociation limits. arb.u., arbitrary unit.
Mentions: In contrast, here we present the direct observation of temporal evolution of the EWP in a nitrogen molecule by the attosecond-pump/attosecond-probe method using nonlinear Fourier transform spectroscopy (NFTS) (27). The scheme for observing the EWP in N2 is shown schematically in Fig. 1A. The potential energy curves of electronic states relevant to the EWP formation are shown in Fig. 1B with the harmonic distribution of a-few-pulse attosecond pulse train (APT) composed of a few attosecond pulses in the envelope. The pump pulse creates a coherent EWP among the bound electronic states in N2 and N2+. Note that the latter involves the ejection of a photoelectron. The probe pulse excites all electronic states involved in the EWP to respective dissociative electronic states in N2+ and triggers fragmentation to generate the N+ ion. The pump-probe delay-dependent kinetic energy (KE) distribution of N+ exhibits at least four characteristic oscillations from 500 as to 3.5 fs ascribed to the electronic motion or charge oscillation between two electronic states.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Attosecond Science Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.

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.

No MeSH data available.


Related in: MedlinePlus