Optical Probing of Single Molecules of Terrylene in a Shpol'kii Matrix: A Two-State Single-Molecule Switch

Moerner, W. E.; Plakhotnik, Taras; Irngartinger, Thomas; Croci, Mirko; Palm, V.; Wild, Urs P.

doi:10.1021/j100081a025

Cited by 162 publications

(84 citation statements)

References 5 publications

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“…For the case of sample heating by the excitation laser, the temperature dependence of the chromophore absorption linewidth would be strongly nonlinear and its limit at T 0 would be larger than the radiative one. But the above value of G 0 is in good agreement with earlier results of lifetime measurements [21].…”

supporting

confidence: 92%

Electronic Energy Relaxation and Transition Frequency Jumps of Single Molecules at 30 mK

Plakhotnik

Donley²,

Kharlamov³

2001

Phys. Rev. Lett.

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Transition frequency jumps for single terrylene molecules in a polyethylene matrix caused by resonant laser irradiation are investigated at 30 mK. These jumps are not accompanied by substantial sample heating. A model for the effect is proposed, based on the interaction of tunneling two-level systems (TLSs) surrounding the single molecule with high-energy nonthermal phonons emitted by the molecule during electronic energy relaxation. The radius of the effective interaction volume is estimated to be r m ഠ 12.5 nm, and the interaction cross section for nonequilibrium phonon -TLS scattering is estimated as ϳ10 222 cm 2 . DOI: 10.1103/PhysRevLett.87.015504 PACS numbers: 61.43.Fs, 78.40. -q The low-temperature properties of glasses have strong anomalies as compared to crystals [1][2][3]. These anomalies are successfully described by the tunneling two-level system (TLS) model, which assumes the existence of a special kind of local low-energy excitations with a very broad distribution of energies and relaxation rates. Phonon assisted TLS dynamics is thought to be responsible for many anomalous properties of glasses at low temperatures and has been the subject of extensive investigation by various methods for almost 30 years. One tool used for the investigation of these dynamics is optical spectroscopy, in particular, photon echo, hole burning, and single-molecule spectroscopy (SMS) (see reviews [4 -13]). All of these methods use a chromophore impurity as a probe whose resonance frequency is subject to spectral diffusion (SD) because of interactions between the probe and TLSs. In principle, impurities can disturb the matrix structure, but there is no indication that impurities at low and moderate concentrations affect the TLS density. An increase of the rate of SD has been detected in samples only at chromophore concentrations above 10 22 mol͞l [14]. Another expected effect of impurity molecules on their local environments could arise from light absorbed by the chromophore. Through subsequent decay processes the absorbed energy is inevitably partially converted to high-energy phonons, which spread into the surrounding space, exciting TLSs and finally decaying into thermal equilibrium phonons. TLS excitation via high-energy phonons was suggested in [14] as a reason for a specific SD time dependence in highly concentrated samples, but no direct evidence for this effect was obtained. The advantage of SMS in measurements of such a kind is that one and the same molecule serves as a phonon generator and as a probe. Therefore, the measurements can be carried out at a low concentration of chromophores, which does not disturb the structure of the matrix. The present work is a first attempt at direct investigation of the influence of highenergy phonons emitted by impurity molecules on their local environments.Experiments were performed on the sample used in previous works [15,16]. The sample has a sandwich structure. A thin layer (about 1 mm thick) of polyethylene (PE) doped with terrylene at a concentration of ϳ10 26 M was p...

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supporting

confidence: 92%

Electronic Energy Relaxation and Transition Frequency Jumps of Single Molecules at 30 mK

Plakhotnik

Donley²,

Kharlamov³

2001

Phys. Rev. Lett.

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“…3 by observing the same SM. Such jumps have been observed under both OPE and TPE and have already been reported for other Shpol'skii systems [31]. Because of these dynamics and conventional photobleaching, the molecular ensemble under study usually changes after one or two hours, even if the spectral range and the laser beam position are preserved.…”

Section: Physical Chemistry Laboratory Swiss Federal Institute Of Tesupporting

confidence: 52%

Time Resolved Single Molecule Spectroscopy

Plakhotnik¹,

Walser²

1998

Phys. Rev. Lett.

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A new method based on the calculation of autocorrelation functions for spectra measured at a high acquisition rate is developed to study spectral dynamics of single molecules. The technique allows for spectroscopy with time resolutions down to the luminescence lifetime. The method is used to study spectral diffusion in two-photon excitation spectra of diphenyloctatetraene molecules doped in an n-tetradecane crystal matrix. The diffusion is light induced, and is absent in one-photon excitation spectra. It has a "steplike" time behavior, different from gradual diffusion observed in glasses.[ S0031-9007(98) Time resolution in SM spectroscopy is also desirable, for example, to study SM interactions with an environment which cause time dependent resonance frequency changes or so-called spectral diffusion (SD). According to the two-level systems (TLSs) model, which was suggested for amorphous solids [13,14] to explain their acoustic and thermodynamic properties, expanded later to include optical phenomena [15], and confirmed in many experiments [16,17], the environment is imitated by a set of TLSs with flip rates distributed from microhertz to gigahertz. A study of fast dynamics requires high time resolution, but it has been considered impossible to implement high time resolution spectroscopy for SMs so far, because the number of detected photons emitted by a SM is small and to first approximation fluctuates according to a Poisson distribution. Even when the exciting laser power saturates the transition and the emission rate is at maximum, a SM signal rarely reaches 10 5 counts͞s (a strong emitter is terrylene [18]). To measure the SM linewidth, the laser intensity should be well below the saturation value. So, only 10 4 counts͞s are detected. To determine the line shape, the recording time should be on the order of 10 ms in the best case. For molecules with 100 times lower emission rate [pentacene, diphenyloctatetraene (DPOT), and many others], this time can be as long as a few seconds. A conventional photon correlation technique [19,20] allows one to gain insight into fast SM dynamics but does not provide spectral information.In this paper, a new approach to SM spectroscopy is reported which pushes the time resolution far below one second, even for molecules with poor emission rates. This technique, which we call intensity-time-frequency correlation (ITFC) SM spectroscopy, can yield microsecond or even better time resolution with an intrinsic theoretical limit at the luminescence lifetime. The ITFC technique is used for studying dynamics in two-photon excitation (TPE) spectra of DPOT molecules in an n-tetradecane matrix [21], where a significant difference between the linewidths in one-photon excitation (OPE) and TPE spectra was observed and tentatively explained by SD induced by the powerful laser illumination required for TPE [22,23]. This explanation agrees with the significant line broadening observed for OPE data in the presence of infrared illumination [24].ITFC spectroscopy works as follows. Instead of record...

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“…3). Such jumps of a SM line frequency in a Shpol'skii matrix were reported in [6]. The laser power dependence of the jump rate was not studied in this work.…”

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confidence: 82%

Light Induced Single Molecule Frequency Shift

et al. 1996

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A light induced frequency shift of the 0-0 line was measured in two-photon excitation spectra of single diphenyloctatetraene molecules doped in a crystal matrix. The shifts were proportional to the laser power with a slope of about 600 MHz͞W when the laser beam of about 300 mW power was focused to a diameter of 2 mm. Significantly, the observed line broadenings were an order of magnitude smaller than the shifts. The effect is ascribed mainly to a "fast" energy exchange between a local vibration and thermal phonons created by the third harmonic C-H band absorption in the matrix, and partially to an ac Stark shift. [S0031-9007(96)

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Optical Probing of Single Molecules of Terrylene in a Shpol'kii Matrix: A Two-State Single-Molecule Switch

Cited by 162 publications

References 5 publications

Electronic Energy Relaxation and Transition Frequency Jumps of Single Molecules at 30 mK

Electronic Energy Relaxation and Transition Frequency Jumps of Single Molecules at 30 mK

Time Resolved Single Molecule Spectroscopy

Light Induced Single Molecule Frequency Shift

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