Observation of Coherent Transient Birefringence in C<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">S</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Vapor

Heritage, J. P.; Gustafson, T. K.; Lin, Chu‐Hsing

doi:10.1103/physrevlett.34.1299

Cited by 142 publications

(60 citation statements)

References 7 publications

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“…An important milestone in the development of alignment methods is the use of linearly polarized, ultrashort laser pulses to create a rotational wave packet by an impulsive Raman mechanism. If the temporal pulse width of the laser is shorter than the rotational period of the molecule (i.e., if its bandwidth is greater than the rotational level spacing), the molecule undergoes a series of Raman excitations that produce a coherent superposition of rotational states [6]. For short pulses, peak field-free alignment along the electric vector of the laser field is achieved after termination of the laser pulse, at a time that depends on the pulse strength.…”

Section: Introductionmentioning

confidence: 99%

Enhanced molecular orientation induced by molecular antialignment

2006

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We explore the role of laser induced anti-alignment in enhancing molecular orientation. A field-free enhanced orientation via anti-alignment scheme is presented, which combines a linearly polarized femtosecond laser pulse with a half-cycle pulse. The laser pulse induces transient anti-alignment in the plane orthogonal to the field polarization, while the half-cycle pulse leads to the orientation. We identify two qualitatively different enhancement mechanisms depending on the pulse order, and optimize their effects using classical and quantum models both at zero and non-zero temperature.

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Section: Introductionmentioning

confidence: 99%

Enhanced molecular orientation induced by molecular antialignment

2006

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“…Field-free one-dimensional alignment, i.e., alignment of a single molecular axis, was achieved using a short laser pulse [4,5], and by the rapid turn off of an adiabatic strong laser field [6]. In these experiments, maximal alignment is produced after the pulse [4,7] when the molecule is field-free, followed by periodic revivals of the rotational wave packet [4]. The rotational energy level spacings for asymmetric tops are much less regular than for linear and symmetric top molecules.…”

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confidence: 99%

Field-Free Three-Dimensional Alignment of Polyatomic Molecules

et al. 2006

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We experimentally demonstrate field-free, three-dimensional alignment (FF3DA) of polyatomic asymmetric top molecules. We achieve FF3DA in sulfur dioxide gas using two time-delayed, orthogonally polarized, nonresonant, femtosecond laser pulses. Our method avoids the use of rotational revivals and is therefore more robust to temperature. The alignment is probed using time-delayed coincidence Coulomb explosion imaging. FF3DA will be important for all molecular imaging, dynamics, or spectroscopy experiments for which random alignment leads to a loss of information. DOI: 10.1103/PhysRevLett.97.173001 PACS numbers: 33.15.Bh, 33.55.Be, 33.80.ÿb The random alignment of gas phase molecules generally reduces the information content of a measurement made in the laboratory frame. The situation is analogous to the well-known case of powder, as opposed to crystal, x-ray diffraction. To ameliorate this situation, it is necessary to define the direction of the molecules in the lab frame prior to making a measurement. Polyatomic molecules are generally asymmetric rotors with three distinct axes of rotation. Three-dimensional alignment, i.e., the alignment of all three molecular axes, was achieved in the presence of an aligning laser field [1,2], but this field strongly perturbs the system, distorting the electronic and vibrational structure of the molecule [3] and preventing the measurement of innate molecular properties. Field-free one-dimensional alignment, i.e., alignment of a single molecular axis, was achieved using a short laser pulse [4,5], and by the rapid turn off of an adiabatic strong laser field [6]. In these experiments, maximal alignment is produced after the pulse [4,7] when the molecule is field-free, followed by periodic revivals of the rotational wave packet [4]. The rotational energy level spacings for asymmetric tops are much less regular than for linear and symmetric top molecules. This complicates the rotational wave-packet evolution for asymmetric rotors, reducing alignment at revivals. The degradation of alignment worsens at elevated rotational temperatures due to the incoherent contributions of thermally populated rotational states which can lead to complete obfuscation of the rotational revival structure. This is a challenge for experimentalists since rotational cooling is often compromised in order to produce sufficiently dense molecular beams.Here we report the experimental demonstration of a general, flexible, and robust method for producing fieldfree, three-dimensional alignment (FF3DA) of polyatomic molecules. This method makes use of the prompt alignment occurring just after the laser pulse and is much more robust with respect to temperature effects than is an earlier proposal for FF3DA at rotational revivals [8]. This technique is broadly applicable and we demonstrate it here for the asymmetric top molecule SO 2 .Our method is based upon the use of two time-separated, perpendicularly polarized, nonresonant, femtosecond laser pulses. The first laser pulse produces postpulse 1D alignment of the...

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“…The full rotational recurrence of CS 2 is expected at 76.5 ps. 34,37 When the laser pulses are weak, this feature can be observed and accurate rotational constants can be determined. 37,[40][41][42][43][44] In Figure 3a, we show experimental data for the case when all laser pulses are weak.…”

Section: A Evidence Of Alignment and Structuralmentioning

confidence: 99%

“…Research from our group has taken advantage of the experimental measurement of rotational recurrences following the formation of an off-resonance polarization transient grating, a method introduced by Heritage et al 34 With femtosecond pulses one is able to make much more accurate determinations of rotational constants and hence better determination of molecular structure. [35][36][37] Soon after, we recognized that the transient grating method would allow us to measure alignment and molecular deformation induced by the strong off-resonance field provided the third pulse (the probe) was kept at a low and constant intensity while the first two pulses, which coincide in time and form the transient grating, provide the strong field.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Laser Induced Molecular Alignment and Deformation: Experimental Evidence from Neutral Molecules and from Fragment Ions

2003

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The alignment and molecular structure deformations induced by intense off-resonance excitation with ultrafast laser pulses are examined using femtosecond transient grating spectroscopy and by angle resolved multiphoton ionization in a molecular beam. The goal of this study is to correlate evidence obtained from the angular dependence of multiphoton ionization and from rotational recurrences observed in neutral molecules regarding alignment and molecular structure deformation. Structural parameters are determined by analysis of the fieldfree rotational recurrences, obtained by transient grating measurements, or by analysis of the anisotropy in the detected fragment ions, in the molecular beam experiments. Experimental data were obtained for CS 2 , CO 2 , acetylene, and benzene, for pulse intensities ranging from 10 11 to 10 14 W/cm 2 . The experimental results are consistent with molecular alignment resulting from a "kick" induced by the ultrafast off-resonance field. The results also provide evidence of molecular structure deformations. Results from transient grating experiments indicate that the electric field can induce alignment and bending in polyatomic molecules and that these effects can take place in the absence of ionization.

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Observation of Coherent Transient Birefringence in CS2Vapor

Cited by 142 publications

References 7 publications

Enhanced molecular orientation induced by molecular antialignment

Enhanced molecular orientation induced by molecular antialignment

Field-Free Three-Dimensional Alignment of Polyatomic Molecules

Ultrafast Laser Induced Molecular Alignment and Deformation: Experimental Evidence from Neutral Molecules and from Fragment Ions

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