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Duration of an intense laser pulse can determine the breakage of multiple chemical bonds.

Xie X, Lötstedt E, Roither S, Schöffler M, Kartashov D, Midorikawa K, Baltuška A, Yamanouchi K, Kitzler M - Sci Rep (2015)

Bottom Line: Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades.With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation.Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion.

View Article: PubMed Central - PubMed

Affiliation: Photonics Institute, Vienna University of Technology, Gusshausstrasse 27, A-1040 Vienna, Austria, EU.

ABSTRACT
Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades. With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation. So far, all successful demonstrations in this area considered only fragmentation reactions, where only one bond is broken and the molecule is split into merely two moieties. Here, using ethylene (C2H4) as an example, we experimentally investigate whether complex fragmentation reactions that involve the breakage of more than one chemical bond can be influenced by parameters of an ultrashort intense laser pulse. We show that the dynamics of removing three electrons by strong-field ionization determines the ratio of fragmentation of the molecular trication into two respectively three moieties. We observe a relative increase of two-body fragmentations with the laser pulse duration by almost an order of magnitude. Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion.

No MeSH data available.


Related in: MedlinePlus

(a) Momentum correlation map for the final products . (b) Fragmentation yield over proton momentum and the asymmetry parameter A as defined in the text for the final products . (c) Momentum distribution in the laser polarization plane for the reaction shown in (b). (d,e) Proton spectra in the laser polarization plane decomposed from (c) based on the asymmetry parameter A. The proton spectra ejected via the concerted () and sequential () fragmentation pathway are shown (d) and (e), respectively. The laser pulse duration and peak intensity are 25 fs and 8 × 1014W/cm2 for all panels. Here and throughout the paper a.u. denotes atomic units.
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f1: (a) Momentum correlation map for the final products . (b) Fragmentation yield over proton momentum and the asymmetry parameter A as defined in the text for the final products . (c) Momentum distribution in the laser polarization plane for the reaction shown in (b). (d,e) Proton spectra in the laser polarization plane decomposed from (c) based on the asymmetry parameter A. The proton spectra ejected via the concerted () and sequential () fragmentation pathway are shown (d) and (e), respectively. The laser pulse duration and peak intensity are 25 fs and 8 × 1014W/cm2 for all panels. Here and throughout the paper a.u. denotes atomic units.

Mentions: As mentioned above, the dynamics of a three-body fragmentation reaction can take place concertedly or sequentially. Conclusive insight into the dynamics can be gained from momentum correlation maps1322. Such a map is depicted in Fig. 1(a) for the channel (3). It shows the absolute values of the momenta of the two fragments H+ and with the momentum of the third fragment, CH+, integrated over. The map exhibits two distinct regions. In region R1 the proton momentum is largely independent of that of the fragment . This indicates that the two fragments are generated during two independent fragmentation steps. Also the proton exhibits high momentum (corresponding to a mean energy of about 8.6 eV), which implies that it is ejected from a high charge state. Thus, region R1 corresponds to a sequential fragmentation reaction, during which a proton is ejected during the first fragmentation step, see Eq. (5)


Duration of an intense laser pulse can determine the breakage of multiple chemical bonds.

Xie X, Lötstedt E, Roither S, Schöffler M, Kartashov D, Midorikawa K, Baltuška A, Yamanouchi K, Kitzler M - Sci Rep (2015)

(a) Momentum correlation map for the final products . (b) Fragmentation yield over proton momentum and the asymmetry parameter A as defined in the text for the final products . (c) Momentum distribution in the laser polarization plane for the reaction shown in (b). (d,e) Proton spectra in the laser polarization plane decomposed from (c) based on the asymmetry parameter A. The proton spectra ejected via the concerted () and sequential () fragmentation pathway are shown (d) and (e), respectively. The laser pulse duration and peak intensity are 25 fs and 8 × 1014W/cm2 for all panels. Here and throughout the paper a.u. denotes atomic units.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4536518&req=5

f1: (a) Momentum correlation map for the final products . (b) Fragmentation yield over proton momentum and the asymmetry parameter A as defined in the text for the final products . (c) Momentum distribution in the laser polarization plane for the reaction shown in (b). (d,e) Proton spectra in the laser polarization plane decomposed from (c) based on the asymmetry parameter A. The proton spectra ejected via the concerted () and sequential () fragmentation pathway are shown (d) and (e), respectively. The laser pulse duration and peak intensity are 25 fs and 8 × 1014W/cm2 for all panels. Here and throughout the paper a.u. denotes atomic units.
Mentions: As mentioned above, the dynamics of a three-body fragmentation reaction can take place concertedly or sequentially. Conclusive insight into the dynamics can be gained from momentum correlation maps1322. Such a map is depicted in Fig. 1(a) for the channel (3). It shows the absolute values of the momenta of the two fragments H+ and with the momentum of the third fragment, CH+, integrated over. The map exhibits two distinct regions. In region R1 the proton momentum is largely independent of that of the fragment . This indicates that the two fragments are generated during two independent fragmentation steps. Also the proton exhibits high momentum (corresponding to a mean energy of about 8.6 eV), which implies that it is ejected from a high charge state. Thus, region R1 corresponds to a sequential fragmentation reaction, during which a proton is ejected during the first fragmentation step, see Eq. (5)

Bottom Line: Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades.With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation.Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion.

View Article: PubMed Central - PubMed

Affiliation: Photonics Institute, Vienna University of Technology, Gusshausstrasse 27, A-1040 Vienna, Austria, EU.

ABSTRACT
Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades. With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation. So far, all successful demonstrations in this area considered only fragmentation reactions, where only one bond is broken and the molecule is split into merely two moieties. Here, using ethylene (C2H4) as an example, we experimentally investigate whether complex fragmentation reactions that involve the breakage of more than one chemical bond can be influenced by parameters of an ultrashort intense laser pulse. We show that the dynamics of removing three electrons by strong-field ionization determines the ratio of fragmentation of the molecular trication into two respectively three moieties. We observe a relative increase of two-body fragmentations with the laser pulse duration by almost an order of magnitude. Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion.

No MeSH data available.


Related in: MedlinePlus