Following a chemical reaction using high-harmonic interferometry

Wörner, H. J.; Bertrand, J. B.; Kartashov, D. V.; Corkum, P. B.; Villeneuve, D. M.
July 2010
Nature;7/29/2010, Vol. 466 Issue 7306, p604
Academic Journal
The study of chemical reactions on the molecular (femtosecond) timescale typically uses pump laser pulses to excite molecules and subsequent probe pulses to interrogate them. The ultrashort pump pulse can excite only a small fraction of molecules, and the probe wavelength must be carefully chosen to discriminate between excited and unexcited molecules. The past decade has seen the emergence of new methods that are also aimed at imaging chemical reactions as they occur, based on X-ray diffraction, electron diffraction or laser-induced recollision—with spectral selection not available for any of these new methods. Here we show that in the case of high-harmonic spectroscopy based on recollision, this apparent limitation becomes a major advantage owing to the coherent nature of the attosecond high-harmonic pulse generation. The coherence allows the unexcited molecules to act as local oscillators against which the dynamics are observed, so a transient grating technique can be used to reconstruct the amplitude and phase of emission from the excited molecules. We then extract structural information from the amplitude, which encodes the internuclear separation, by quantum interference at short times and by scattering of the recollision electron at longer times. The phase records the attosecond dynamics of the electrons, giving access to the evolving ionization potentials and the electronic structure of the transient molecule. In our experiment, we are able to document a temporal shift of the high-harmonic field of less than an attosecond (1 as = 10−18 s) between the stretched and compressed geometry of weakly vibrationally excited Br2 in the electronic ground state. The ability to probe structural and electronic features, combined with high time resolution, make high-harmonic spectroscopy ideally suited to measuring coupled electronic and nuclear dynamics occurring in photochemical reactions and to characterizing the electronic structure of transition states.


Related Articles

  • Wanted: simple methods for complex measurements. Bowlan, Pamela; Gabolde, Pablo; Trebino, Rick // Laser Focus World;Jun2007, Vol. 43 Issue 6, p105 

    The article provides simple devices that can measure complex light pulses in time and space. The first device is name SEA TADPOLE, which involves measuring the spectrum of the sum of the unknown and reference pulses, a type of spectral interferometry. The second device is name STRIPED FISH,...

  • Primary events in the photodissociation of oxyhemoglobin. Yabushita, Atsushi; Kobayashi, Takayoshi // Spectroscopy: An International Journal;2010, Vol. 24 Issue 3/4, p333 

    The growing number of data on heme proteins in the ultrafast time domain have revealed complicated photophysics of the heme that are sensitive both to the structure of the protein and to the ligand species. In this work, ultrafast time-resolved pump–probe in visible spectral range was...

  • Formation of In-(2×1) and In islands on Si(100)-(2×1) by femtosecond pulsed laser deposition. Hafez, M. A.; Elsayed-Ali, H. E. // Journal of Applied Physics;6/1/2007, Vol. 101 Issue 11, p113515 

    The growth of indium on a vicinal Si(100)-(2×1) surface at room temperature by femtosecond pulsed laser deposition (fsPLD) was investigated by in situ reflection high-energy electron diffraction (RHEED). Recovery of the RHEED intensity was observed between laser pulses and when the growth...

  • Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation. Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H. // Journal of Chemical Physics;11/21/2006, Vol. 125 Issue 19, p194303 

    Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained....

  • Reentrant cone angle dependence of the energetic electron slope temperature in high-intensity laser-plasma interactions. Nakatsutsumi, M.; Kodama, R.; Norreys, P. A.; Awano, S.; Nakamura, H.; Norimatsu, T.; Ooya, A.; Tampo, M.; Tanaka, K. A.; Tanimoto, T.; Tsutsumi, T.; Yabuuchi, T. // Physics of Plasmas;May2007, Vol. 14 Issue 5, p050701 

    Energy spectra of fast electrons, generated when high-intensity laser pulses irradiated hollow conical targets, have been measured experimentally. It is shown here that the slope temperature of the fast electrons is strongly dependent on the opening angle of the cone, and has a maximum value at...

  • Experimental diagnostic module for ultrafast combined interferometry of the processes of interaction of ultrashort laser pulses with condensed media in vacuum. Loktionov, E. Yu.; Ovchinnikov, A. V.; Protasov, Yu. Yu.; Sitnikov, D. S. // Instruments & Experimental Techniques;May2010, Vol. 53 Issue 3, p416 

    An experimental diagnostic module based on a femtosecond laser system (τ0.5 ∼ 45-70 fs, 7n = 266, 400, and 800 nm) and the experimental technique for ultrafast combined interferometric investigation of the interaction of ultrashort laser pulses with condensed media in vacuum are...

  • Picosecond three-color holographic digital interferometry. Redkorechev, V. I.; Kulagin, I. A.; Gurevich, V. S.; Gusev, M. E.; Zakharov, Yu. N. // Optics & Spectroscopy;Sep2009, Vol. 107 Issue 3, p407 

    The possibilities of multicolor digital holographic interferometry are experimentally studied upon measuring displacements of a surface in radiation of a picosecond Nd:YAG laser with the radiation frequency conversion into harmonics (λ1 = 1.06 µm, λ2 = 0.53 µm, and λ3 = 0.35...

  • Dispersion of femtosecond laser pulses in beam pipelines from ambient pressure to 0.1 mbar. Osvay, K.; Börzsönyi, Á.; Kovács, A.P.; Görbe, M.; Kurdi, G.; Kalashnikov, M.P. // Applied Physics B: Lasers & Optics;May2007, Vol. 87 Issue 3, p457 

    Dispersion of femtosecond pulses in evacuated laser pipelines was measured by spectrally and spatially resolved interferometry. The pressure range varied from 1 bar to 0.1 mbar. The change of spectral phase has been experimentally proven to follow the Edlén-type dispersion formula....

  • Generation and detection of ultrashort pulses of electromagnetic field in the terahertz range and their application for spectroscopy. Akhmedzhanov, R. A.; Korytin, A. I.; Litvak, A. G.; Sergeev, A. M.; Suvorov, E. V. // Radiophysics & Quantum Electronics;Oct/Nov2005, Vol. 48 Issue 10/11, p837 

    We present experimental results on generation of pulsed terahertz radiation in a ZnTe crystal using nonlinear optical rectification of high-power femtosecond laser pulses. The use of terahertz pulses for spectroscopy is tested in the rotational lines of absorption of water vapors in the...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics