Temperature-dependent kinetics of photophysical hole burning in a tetracene-doped mthf glass (original) (raw)
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Persistent Infrared Spectral Hole Burning of Impurity Vibrational Modes in Chalcogenide Glasses
Pusisttnt In/rared spectral hole burning of impurity vibrational modts is used to study host-defect dynamics in chalcogenide glasses. the first class 0/ glas~ systems to ahibit non-t1tctronic persistent hole burning. New hole burmng systems identified include the CO 2 , D 2 0, OD. and SH moltcules in AsrSJ; CO 2 and SeH in QIfIOrplww St; and StH in As,seJ. Basic principles of persistent spectral hole burning are rtviewtd and dttails of applying the technique in the mid-infrartd using Itad-salt stmiconductor diode lasers are discussed. Results for the various systems are consistent with local host restructuring as the hole burning mechanism, and show thallhe host determines both lhe non-exponential spontaneous hole filling and the remperaturt•dqJen.dt11l optical dephasing bthavlors. 28 S. P. Love.t A. J. Sievers to many hOlm or even days. The utility of the phenomenon lics in the fact that. because only those centers in resonance with the laser are involved in the hole burning. it is possible to ClI.traCt the lifetime-limited homogeneous linewidth, which would ordinarily be obscured within the disorder-dominated inhomogeneous absorption band. Furthermore, because in glasses the hole burning process itself is intimately connected with the existence of multiple metaslable configurations of the glass. it is possible. by studying the time evolution of the spectral hole. to learn about the low temperature relaxation dynamics among these glassy configurations. Persistent spectral hole burning is to be contrasted with the older technique of transient satunltion hole buming,l.l The latter is a high intensity technique. requiring thilt the rate at which photons are absorbed be comparable to the rale at which the impurities relax back to their ground state; intensities used are typically several kW/cm 2 • and these holes persist only as long as the excited state lifetime. typically on the order of a nanosecond. In persistent spectral hole burning. high laser intensities are not required. The long lifetime of the effect makes it possible for a spectral hole to gradually build up over time. even at low imensity. Typical cw lascr intensities for the work reponed here range from a few mW/cm 2 10 roughly 100 mW/cm 2. The earliest instances of persistent spectral burning involved electronic transitions of organic dyes in amorphous organic matrices. These first observations were reponed in 1974 by Gorolchovskii et al. 3 for free-base phthalocyanine in a frozen n-octane matrix. and by Kharlamov et al.• for perylene and 9-aminoacridine in glassy ethanol matrices. Since these initial discoveries. numerous other ellamples of systems exhibiting PSHB for impurity elecbonic transitions have been discovered both in other organic systems s and in inorganic systems such as rare eanh ions in silicate glasscs. 6 In the course of these discoveries. it became clear that there were several mechanisms by which PSHB could occur. These mechanisms lend 10 fall within two broad categories: photochemical hole burning (PHB), in which the laser induces a change in the electronic propenies of the impurity molecule itself. breaking a bond for example. and non-photochemical hole burning (NPHB). in which the impurity molecule remains essentially unchanged but either it reorients or the host matrix around it changes. It is this latter type of hole burning which is will be of interest here. All the early NPHB systems mentioned above involved electronic transitions of the impurity molecules. with photon energies on the order of 2 eV. This class of systems has continued to be a major focus of persistent hole burning studies. in part due to the availability of tunable dye lasers in the visible region. In view of the large penuroation associated with electronic e"citation. however, it is unclear whether behavior probed using electronic spectral hole burning is representative of the unpenurbed glass. J[ remained to be seen whether PSHB. and in panicular NPHB. was possible for the much lower energy infrared transitions associated with e"citation of impurity vibrational Persistenllnfrared Spectral Hole BUrning or. ..
Influence of the experimental parameters on time-resolved transient hole-burning
Chemical Physics Letters, 1990
The influence of the burning power, burning time and probe power on the holewidth, hole depth and hole decay time have been studied in time-resolved transient hole-burning (THB) experiments. The systems investigated are free-base polphin (HI,P) in crystalline n-octane (n-C,), zinc-porphin (ZnP) in n-Cs, and ZnP in amorphous polyethylene (PE). The THB kinetics is interpreted in terms of saturation broadening due to a triplet state bottleneck. The holewidtb and decay time of the hole arc not influenced by the probe power, FJA, at least for P,/A< 10 pW/mm'. The same hole-broadening kinetics has been found to apply for the crystalline and the amorphous hosts here studied.
Spectral diffusion in organic glasses. Temperature dependence of permanent and transient holes
Chemical Physics Letters, 1993
Spectral diffusion of the S, tSo O-O transition (a) of bacteriochlorophyll a (BChl a) as guest in the glasses ethanol (EtOH), triethylamine (TEA), 2-methyltetrahydrofuran (MTHF) and diethylether at low temperature has been studied by transient and permanent hole burning with a single-mode GaAlAs diode laser at = 780 nm. Transient holes decay on a time scale of about 100 ms, determined by the triplet-state lifetime of BChl a. Their widths are compared to those of permanent holes probed on a time
1999
A new effect in doped organic glasses, which we refer to as ''energy transfer ͑ET͒-induced spectral diffusion ͑SD͒,'' ET→SD, has recently been reported by us. In this process ''extra'' SD, in addition to ''normal'' SD in glasses, is triggered by the energy balance released on ''downhill'' ET. Quantitative aspects of the ET→SD process have been investigated by means of time-resolved hole-burning experiments on free-base chlorin (H 2 Ch) in polystyrene ͑PS͒ presented here. The ''effective'' homogeneous linewidth ⌫ hom Ј was determined as a function of delay time t d (10 Ϫ5 Ϫ10 3 s), temperature ͑1.2 to 4.2 K͒ and concentration (cϭ1ϫ10 Ϫ5 to 6ϫ10 3 M), at various excitation wavelengths within the S 1 ←S 0 0-0 band. ⌫ hom Ј as a function of temperature was found to obey the relation ⌫ hom Ј ϭ⌫ 0 ЈϩaT 1.3 , characteristic for glasses, and we present an analysis of the residual linewidth ⌫ 0 Ј and the coupling constant a. In this analysis we determined ͑i͒ the separate contributions to ⌫ 0 Ј arising from the fluorescence lifetime, ET, and ET→SD, ͑ii͒ the separate contributions to a arising from ''pure'' dephasing, ''normal'' SD, and ''extra'' spectral diffusion caused by ET→SD. The contributions of ET→SD to ⌫ 0 Ј and a prove to be proportional to the concentration and to the logarithm of the delay time (ϰc log t d).
1998
Ž. Ž. We discovered a remarkable effect: spectral diffusion SD induced by energy transfer ET , here called ET ™ SD. The X Ž. Ž. 'effective' homogeneous linewidth G of the S § S 0-0 band of free-base chlorin H Ch in polystyrene PS was hom 1 0 2 followed as a function of concentration and excitation wavelength by hole-burning. The results cannot simply be explained Ž. X by Forster's ET mechanism: 1 the increase of G towards the blue is larger than expected and follows an S-shaped hom Ž. X Ž. curve; 2 G increases linearly with concentration; and 3 the holes are Lorentzian. A model is proposed which predicts hom that G X should increase with delay time, even at T ™ 0. This is confirmed by experiments.
Spectral hole burning in thulium-doped glass ceramics
Optics Letters, 2001
We have used spectral hole burning to measure the homogeneous linewidth of the 3 H 6 ͑1͒ 3 F 3 ͑1͒ transition of Tm 31 ions doped into oxyf luoride glass ceramics consisting of nanocrystals of LaF 3 in an aluminosilicate glass matrix. From the magnitude of the hole width in the nanocrystals and its dependence on temperature, we propose that excitation of tunneling modes in the adjacent glassy phase as well as of confined mechanical modes in the nanocrystals is responsible for the broadening.
Spectral diffusion in glasses under high pressure: A study by time-resolved hole-burning
The Journal of Chemical Physics, 1999
We have studied optical dephasing and spectral diffusion of the S 1 ←S 0 0-0 transition of bacteriochlorophyll-a (BChl-a) in the glass 2-methyltetrahydrofuran ͑MTHF͒ at ambient (⌬p ϭ0) and high pressure (⌬pϭ3.6 GPa) between 1.2 and 4.2 K by time-resolved hole-burning. The ''effective'' homogeneous linewidth ⌫ hom Ј follows a power law dependence on temperature, ⌫ hom Ј ϭ⌫ 0 ЈϩaT 1.3Ϯ0.1 , where ⌫ 0 Јϭ⌫ 0 ϩ⌫ 0 ET ϩ⌫ 0 ET→SD (t d) is the residual linewidth and aϭa PD ϩa SD (t d)ϩa ET→SD (t d) is the coupling constant. The separate contributions to ⌫ 0 Ј and a are the fluorescence decay rate ⌫ 0 ϭ(2 fl) Ϫ1 , the ''downhill'' energy-transfer rate ⌫ 0 ET , the coupling constants due to ''pure'' dephasing a PD and ''normal'' spectral diffusion a SD (t d), and two terms related to ''extra'' spectral diffusion induced by energy transfer, ⌫ 0 ET→SD (t d) and a ET→SD (t d). We have quantitatively analyzed these contributions at ambient and high pressure. The results show that ''normal'' SD, ''extra'' SD, and ET→SD are strongly influenced by pressure. We have interpreted our findings in terms of a change in the number of two-level-systems, the low-frequency modes characteristic for the glassy state.
Spectral Diffusion in Organic Glasses: Time Dependence of Spectral Holes
The Journal of Physical Chemistry, 1996
Time-resolved spectral hole-burning experiments have been performed to probe the dynamics of the S 1 r S 0 0-0 transition of bacteriochlorophyll-a at low concentration (1 × 10-5 M) in four different glasses (2-methyltetrahydrofuran, protonated and deuterated ethanol, diethyl ether, and triethylamine) as a function of delay time t d (from 10-6 to 10 3 s) and temperature T (1.2-4.2 K). It is shown that spectral diffusion, the broadening of the optical linewidth followed here over nine orders of magnitude in time, increases with temperature as T 1.3(0.1 and strongly depends on the glass structure. The functional dependence, however, is not influenced by the specific glass. The variation of the "effective" homogeneous linewidth (Γ′ hom) with T and t d is described by a function Γ′ hom (T,t d) derived by modifying the standard model of two-level systems (TLS). This revised TLS model, in which the distribution functions of the TLS tunneling parameters are different from those in the standard model, takes into account the common origin of the dependence of Γ′ hom on t d and T. It is shown that other hole-burning and photon-echo data reported in the literature can also be fitted by the same function Γ′ hom (T,t d). In ethanol glass, the number of TLSs and the amount of spectral diffusion appear to be independent of the probe molecule.
Photon-gated hole burning: a new mechanism using two-step photoionization
Optics Letters, 1985
We have observed photon-gated spectral hole burning, i.e., hole burning that occurs only in the presence of an additional gating-light source. Gating enhancement factors of 104 were observed. In BaClF:Sm2+ this involves twostep photoionization of Sm 2 + and leads to persistent holes in the 4 Fo-5 Do (687.9-nm) and 7 Fo-5 D 1 (629.7-nm) absorption lines. The hole widths of 25 MHz at 2 K are much narrower than the inhomogeneous broadening of 16 GHz. The action spectrum of the gating shows a threshold behavior around 2.5 eV. Erasing studies show that Sm 3 + acts as a trap for the released electrons. A remarkable and novel feature is that the holes can be recovered after temperature cycling to 300 K.
1988
Spectral holes have been burnt in the S, Go O-O transition of resorufin in polymethylmethacrylate (PMMA) and glycerol, and of free-base porphin (H,P) in PMMA and polyethylene (PE). The holewidths follow a T 'J dependence over almost two orders of magnitude in temperature and extrapolate to the fluorescence lifetime-limited value of each guest when T-0. The discrepancy between the holewidths of resorufin in glycerol presented here and those reported in the literature are attributed to burning fluences. Photon-echo and hole-burning results are compared. Optical dephasing data are interpreted in terms of low-frequency localized phonon modes and are critically discussed.