The femtosecond birefringence of CO2: from the high pressure gas to the liquid phase

Zhou, Y.; Constantine, S.; Harrel, S.; Gardecki, J. A.; Ziegler, L. D.

doi:10.1002/(sici)1097-4555(200001/02)31:1/2<85::aid-jrs501>3.3.co;2-c

Cited by 3 publications

(7 citation statements)

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“…In one attempt to identify the nature of these OHD P (3) signals, we measured the OHD−OKE responses of near critical CO 2 and CHF 3 excited by laser pulses at ∼800 or ∼600 nm resulting from a regeneratively amplified laser system operating at 250 kHz. The OHD responses of near critical CO 2 and CHF 3 obtained with these excitation sources exhibited a normal type of birefringent (instantaneous nonresonant electronic and Raman nuclear) and dichroic (weak dispersive-shaped) responses in agreement with our previous OHD−OKE studies of near critical CO 2 …”

Section: Resultssupporting

confidence: 89%

“…The critical temperature for this H 2 solution (CO 2 density = 0.8 ρ C ) is reduced by ∼10 to ∼21 °C from the neat CO 2 T C . Such density dependent features in the region of the nonresonant electronic response were not observed in a previous OHD ultrafast study of the birefringent responses of CO 2 at virtually identical near critical state points using 50 fs pulses at ∼600 nm from an regeneratively amplified Ti:sapphire laser system operating at 100 kHz . As will be shown below the novel time dependent feature observed in the ultrafast OHD responses of the near SCFs studied is due to accumulated, optical heterodyne detected acoustic transient gratings and its prominent appearance in the samples of interest here is attributable to the unique properties of fluids near the SC region as compared to normal liquids.…”

Section: Introductionsupporting

confidence: 47%

“…Laser Configuration. Ultrafast responses were obtained in a two-beam pump−probe setup or a standard two-beam optical heterodyne detected OKE configuration. , As is usual in this OKE configuration, anisotropic dichroic signals (in-phase, φ LO = 0) were obtained by rotating an analyzing polarizer between the sample and the detector, and birefringent (π/2 out-of-phase, φ LO = π/2) signals resulted when the polarizer in front of a quarter wave plate in the probe arm was rotated. Ti:sapphire oscillator pulses at 76 MHz and a variety of pulse widths in the range of 20−45 fs were used to observe the accumulated signals reported here.…”

Section: Methodsmentioning

confidence: 99%

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Optical Heterodyne Detected Accumulated Acoustic Grating Responses in Near Supercritical Fluids

Peng

Ziegler

2007

J. Phys. Chem. A

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A novel third-order polarization effect due to an accumulated optical heterodyne detected (OHD) transient acoustic grating response in near critical fluids was observed and experimentally characterized. Femtosecond pump-probe responses in near critical CO2 and CHF3 illustrate this phenomenon. This large optically generated acoustic response due to electrostrictive coupling appears only when pump and probe pulses are temporally overlapped and is pi out-of-phase with the normal optical Kerr effect (OKE) birefringent signal. The local oscillator, the laser intensity, and the modeled experimental repetition rate dependence identify the accumulated heterodyne origin of these responses. The observed OHD accumulated acoustic birefringent signal is inversely dependent on sound velocity to the fifth power. A corresponding sound velocity dependent dichroic (in-phase) response was also observed for these electronically nonresonant samples. The accumulated effect described here may have applications for the design of efficient modulators and as a simple and sensitive experimental technique for the measurement of near critical fluid thermodynamic and acoustic parameters.

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Section: Resultssupporting

confidence: 89%

Section: Introductionsupporting

confidence: 47%

Section: Methodsmentioning

confidence: 99%

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Optical Heterodyne Detected Accumulated Acoustic Grating Responses in Near Supercritical Fluids

Peng

Ziegler

2007

J. Phys. Chem. A

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“…[21][22][23][24][25][26][27] A full appreciation of the dynamics of a solute molecule requires that the solvent dynamics be fully characterized as well. Although a few noteworthy exceptions appear in the literature, [28][29][30][31][32][33][34][35][36][37] wide-ranging systematic experimental investigations of neat SCFs have not been actively pursued. The extant studies generally have considered only a few selected state points, and for the most part the points selected have been taken to lie well away from the critical point in order to avoid complications such as critical opalescence.…”

Section: Introductionmentioning

confidence: 99%

Rotational Relaxation in Supercritical CO₂

Adams

Siavosh-Haghighi

2002

J. Phys. Chem. B

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Though there are numerous studies of solute molecule rotational dynamics in ordinary liquids and supercritical fluids, few such studies have focused on the molecules of a neat supercritical fluid. In the present study, we investigate the structure and rotational dynamics of supercritical carbon dioxide at a temperature 1% above its critical temperature and over a 20-fold range of densities about the critical density. Our simulations reveal the presence of density inhomogeneities and thus regions of modest local density enhancement in this fluid over a significant range of bulk densities. Although these inhomogeneities account for the weak bulk density dependence of the CO 2 orientational correlation times in the near-critical regime, they are not reflected in a concomitant variation in the observed total rotational friction. Caution is warranted, however, in interpreting the usual diffusive dynamics parameters in this system because only at densities in excess of the critical density may the dynamics be characterized as diffusive; only at lower densities are orientational correlations found to decay on a time scale equal to or shorter than that characterizing the angular velocity correlations.

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“…This is somewhat plausible, given, for example, the B340 fs molecular reorientation time observed for liquid CO 2 . 43 In addition, one might expect reorientation to speed up at the interface. To test the hypothesis that, for 1-heptanol, reorientation is too fast to be resolved, we have studied the reorientational dynamics of 1-dodecanol (CH 3 (CH 2 ) 11 OH) at aqueous interfaces.…”

Section: Resultsmentioning

confidence: 99%

Ultrafast inter- and intramolecular vibrational energy transfer between molecules at interfaces studied by time- and polarization-resolved SFG spectroscopy

Yamamoto

Ghosh

Nienhuys

et al. 2010

Phys. Chem. Chem. Phys.

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We present experimental results on femtosecond time-resolved surface vibrational spectroscopy aimed at elucidating the sub-picosecond reorientational dynamics of surface molecules. The approach, which relies on polarization- and time-resolved surface sum frequency generation (SFG), provides a general means to monitor interfacial reorientational dynamics through vibrations inherent in surface molecules in their electronic ground state. The technique requires an anisotropic vibrational excitation of surface molecules using orthogonally polarized infrared excitation light. The decay of the resulting anisotropy is followed in real-time. We employ the technique to reveal the reorientational dynamics of vibrational transition dipoles of long-chain primary alcohols on the water surface, and of water molecules at the water-air interface. The results demonstrate that, in addition to reorientational motion of specific molecules or molecular groups at the interface, inter- and intramolecular energy transfer processes can serve to scramble the initial anisotropy very efficiently. In the two exemplary cases demonstrated here, energy transfer occurs much faster than reorientational motion of interfacial molecules. This has important implications for the interpretation of static SFG spectra. Finally, we suggest experimental schemes and strategies to decouple effects resulting from energy transfer from those associated with surface molecular motion.

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The femtosecond birefringence of CO2: from the high pressure gas to the liquid phase

Cited by 3 publications

References 0 publications

Optical Heterodyne Detected Accumulated Acoustic Grating Responses in Near Supercritical Fluids

Optical Heterodyne Detected Accumulated Acoustic Grating Responses in Near Supercritical Fluids

Rotational Relaxation in Supercritical CO₂

Ultrafast inter- and intramolecular vibrational energy transfer between molecules at interfaces studied by time- and polarization-resolved SFG spectroscopy

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The femtosecond birefringence of CO2: from the high pressure gas to the liquid phase

Cited by 3 publications

References 0 publications

Optical Heterodyne Detected Accumulated Acoustic Grating Responses in Near Supercritical Fluids

Optical Heterodyne Detected Accumulated Acoustic Grating Responses in Near Supercritical Fluids

Rotational Relaxation in Supercritical CO2

Ultrafast inter- and intramolecular vibrational energy transfer between molecules at interfaces studied by time- and polarization-resolved SFG spectroscopy

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Product

Resources

About

Rotational Relaxation in Supercritical CO₂