Experimental evidence of laser cooling of room temperature <i>trans</i>-stilbene upon excitation to the S1 state

Warmuth, Christian; Milota, Franz; Kauffmann, H. F.; Wadi, Hicham; Pollak, Eli

doi:10.1063/1.480993

Cited by 13 publications

(16 citation statements)

References 21 publications

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“…12 The rate was found to be minimal at the 0 0 0 transition frequency and substantially rising both to a͒ the red and to the blue of the 0 0 0 frequency. 12 The rate was found to be minimal at the 0 0 0 transition frequency and substantially rising both to a͒ the red and to the blue of the 0 0 0 frequency.…”

Section: Introductionmentioning

confidence: 88%

Ab initio spectroscopy and photoinduced cooling of the trans-stilbene molecule

Tatchen

Pollak

2008

The Journal of Chemical Physics

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We present a theoretical study of the S(0)-->S(1) and S(0)<--S(1) vibronic spectra for trans-stilbene. Franck-Condon spectra in the harmonic approximation are generated for the complete system with 72 degrees of freedom by means of an analytic time-dependent approach accounting for Dushinsky rotations and thermal effects. The force fields are computed by means of density functional theory (DFT) and time-dependent DFT, on the one hand, and ab initio complete active space self-consistent field theory, on the other hand. The B3LYP functional shows that almost planar potential energy surface minima are found for the S(0) and S(1) state. Imposing C(2h) symmetry constraints, we obtain low-temperature high-resolution Franck-Condon spectra for both absorption and emission which are in reasonably good agreement with the experimental spectra measured by Syage et al. [J. Chem. Phys. 81, 4685 (1984)] in supersonic jets. Due to thermal population of low-energy modes, the room temperature absorption spectrum is very broad. An almost structureless band which extends over several thousand cm(-1) is obtained from the present theory and agrees with the experimental absorption band shape. Finally, within the harmonic model, we study the effect of photoexcitation on the energy distribution in the excited S(1) state. We find noticeable cooling of approximately 20 K within a frequency interval spanning from -400 to 200 cm(-1) around the 0-0 transition. This indicates that photoinduced cooling must be taken into account when considering the dynamics of the photoinduced isomerization of trans-stilbene. Moreover, this is not the final word, as anharmonicity of the low frequency modes must be taken into account to obtain a full picture which would explain both the energy dependence of the isomerization rates as well as the dependence on the pressure of an external buffer gas.

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Section: Introductionmentioning

confidence: 88%

Ab initio spectroscopy and photoinduced cooling of the trans-stilbene molecule

Tatchen

Pollak

2008

The Journal of Chemical Physics

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“…In recent years evidence for cooling in trans-stilbene has been found by Warmuth et al, 36 who observed a dependence of the isomerization rate on the laser excitation frequency in bulb experiments. Just such an effect would be expected on the basis of the cooling mechanism.…”

Section: Introductionmentioning

confidence: 95%

“…Indeed, spectroscopic evidence for cooling at pressures around 1 atm has been recently reported. 36 Following Gershinsky and Pollak, 19 we can approximately estimate the possible effects of cooling on the isomerization rate by calculating the excess vibrational energy of the molecule Figure 10. Direct comparison of LRMT and experimental isomerization rates for trans-stilbene isotopomers.…”

Section: Thermal Isomerization Ratementioning

confidence: 99%

Quantum Energy Flow andtrans-Stilbene Photoisomerization: an Example of a Non-RRKM Reaction

et al. 2003

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We apply multireference ab initio quantum chemistry and microcanonical transition state (RRKM) theory with quantum energy flow corrections from local random matrix theory (LRMT) to determine the kinetics of trans-stilbene photoisomerization. With a single ab initio potential energy surface and no adjustable parameters, simultaneous agreement with experiment of the microcanonical isomerization rates for the d 0 , d 2 , d 10 , and d 12 isotopomers is obtained. We are also able to reproduce the pressure dependence of the thermal rate. Laser cooling effects on the isomerization rate are calculated and found to be quite small. The S 1 /S 2 energy gap at the transition state is found to be quite large (0.86 eV), suggesting that nonadiabatic effects are negligible. Using the ab initio results in a simple RRKM theory without corrections for finite quantum energy flow does not lead to agreement with experiment. We conclude that non-RRKM effects are essential to understand photoisomerization of trans-stilbene and that these can be predicted using LRMT.

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“…5,10,[18][19][20][21] Hamaguchi proposed a "dynamic polarization model" in which the time evolution is dominated by the stochastic polarization of the mode, induced by the solvent. 18 Kovalenko et al 3 suggested that the change in the dynamics, from broadening of the FWHM at low excitation energies to narrowing at high excitation energies serves as an indication of the initial temperature of the excited mode.…”

Section: Introductionmentioning

confidence: 99%

“…The evolution of this relaxation depends upon many factors such as solute-solvent coupling, intramolecular-vibrationalrelaxation, temperature of the bath and the initial state of the molecule. [1][2][3][4][5][6][7][8][9][10] Many experiments have been carried out to probe the time-dependent vibrational relaxation of the Stilbene molecule. [3][4][5][6][7][8][9][11][12][13][14][15][16][17] The measured data on a given vibrational band are characteristically summarized in terms of the time evolution of the instantaneous maximum of the band and its full width at half maximum (FWHM).…”

Section: Introductionmentioning

confidence: 99%

Energy relaxation of a dissipative quantum oscillator

Kumar

Pollak

2014

The Journal of Chemical Physics

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The dissipative harmonic oscillator is studied as a model for vibrational relaxation in a liquid environment. Continuum limit expressions are derived for the time-dependent average energy, average width of the population, and the vibrational population itself. The effect of the magnitude of the solute-solvent interaction, expressed in terms of a friction coefficient, solvent temperature, and initial energy of the oscillator on the relaxation has been studied. These results shed light on the recent femtosecond stimulated Raman scattering probe of the 1570 cm(-1) -C=C- stretching mode of trans-Stilbene in the first (S1) excited electronic state. When the oscillator is initially cold with respect to the bath temperature, its average energy and width increase in time. When it is initially hot, the average energy and width decrease with time in qualitative agreement with the experimental observations.

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Experimental evidence of laser cooling of room temperature trans-stilbene upon excitation to the S1 state

Cited by 13 publications

References 21 publications

Ab initio spectroscopy and photoinduced cooling of the trans-stilbene molecule

Ab initio spectroscopy and photoinduced cooling of the trans-stilbene molecule

Quantum Energy Flow andtrans-Stilbene Photoisomerization: an Example of a Non-RRKM Reaction

Energy relaxation of a dissipative quantum oscillator

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