UScholar Works
 
Filters: Collection: "ir_uspace" Subject: "Photoinduced absorption"
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CreatorTitleDescriptionSubjectDate
1 Vardeny, Zeev ValentineAbsorption studies of charged excitations in α-sexithiopheneWe present photoexcitation studies of vacuum deposited neutral films of α,ω-substituted sexithiophene (α-6T) using photoinduced absorption (PA) and PAdetected magnetic resonance spectroscopy (PADMR). We find evidence for photoinduced polarons having spin 1/2, with two absorption bands at 0.80...alpha- sexithiophene; Charged excitations; Photoexcitation; Photoinduced absorption1996
2 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Detection of soliton shape modes in polyacetyleneWe observed soliton shape modes by photoinduced absorption in partially isomerized (CH)x and (CD)x, coexisting with the soliton translational modes. The shape modes' ir activity, their dependence on the degree of isomerization, and the photoinduced spectra are explained in detail by a symmetry-break...Soliton shape modes; Polyacetylene; Photoinduced absorption1986-12
3 Vardeny, Zeev ValentineElectromodulation of charge-transfer photoexcitations in pristine and C60-doped conjugated polymersWe study the effect of an electric field of up to 100 kV/cm on photoexcitations in pristine and C60-doped p-conjugated polymers by electromodulated photoinduced absorption (EPA). In EPA, we measure changes in the photoinduced absorption of a polymer film induced by an electric field. The dominant ...Electromodulation; Charge-transfer photoexcitations; Photoinduced absorption; pi-conjugated polymers; Electromodulation spectroscopy1999-04
4 Vardeny, Zeev Valentine; Taylor, P. CraigExcitation energy dependence of photoinduced absorption in intrinsic a-Si:HWe have studied subgap absorption of intrinsic a-Si:H induced by below- and above-gap photoexcitation. We find very similar photoinduced subgap absorption spectra when excited with 2.4 eV or 1.2 eV light. Both spectra exhibit a power-law dependence on laser intensity ?T ~ 1a, where a is 0.5 and 0.7...Intrinsic a-Si:H; Subgap absorption; Photoinduced absorption; Gap photoexcitation; Photomodulation; Electronic states1998
5 Vardeny, Zeev Valentine; Gellermann, WernerNear-infrared ps transient photoinduced absorption in conjugated systemsWe demonstrate the use of a color center laser in a pump-and-probe correlation technique which enables us to extend the probe spectral range into the infrared. As a result, we find strong photoinduced infrared absorption in several 7t-conjugated polymers and oligomers. We associate this absorption w...Ultrafast spectroscopy; Color center laser; Photoinduced absorption; Singlet excitons; Even parity states; Odd parity states; Infrared absorption1997
6 Vardeny, Zeev ValentineOptical bias control of dispersive relaxations in α-SI:HRelaxation of the photoinduced ir absorption band in a-Si:H was studied in the microsecond time domain as a function of cw bias illumination. The decays follow a power law t-a where the dispersion parameter a increases with bias illumination. At low temperatures, a increases linearly with the stead...Optical bias; Dispersive relaxations; Amorphous silicon; a-Si:H; Photoinduced absorption; Bias-controlled tunneling; Multiple trapping1984-01
7 Vardeny, Zeev ValentinePhotoconductivity and photoinduced absorption in a-Si:F and a-Si:HThe photoconductivity (PC) and photoinduced absorption (PA) of RF glow discharge a-Si:F and a-Si:H samples is reported. The value of the room temperature PC of a-Si:F is lower by some four orders of magnitude relative to that of a-Si:H, but the PA of a-Si:F is found to be significantly higher than t...Photoinduced absorption; a-Si:F; a-Si:H; RF glow discharge; Spin densities1984
8 Vardeny, Zeev ValentinePhotoexcitation dynamics in C60-doped PPV under bias illuminationWe have studied photoexcitation dynamics in pristine and C60-doped PPV films under bias Olumination by photoinduced absorption (PA), optically-detected magnetic resonance (ODMR), and electromodulated PA (EPA). Intrachain polaron pair species are the dominant excitations under these conditions. The p...Photoexcitation dynamics; C60-doped PPV; Bias illumination; PPV films; Photoinduced absorption; ODMR; Electroabsorption1996
9 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Photogeneration of confined soliton pairs (bipolarons) in polythiopheneFrom photoinduced absorption and light-induced electron-spin resonance, we demonstrate that the dominant photocarriers generated in polythiophene with excitation above the energy gap (Eg) are charged bipolarons (spin 0). The observation of bipolarons (B2± ) rather than polarons (Pf ) as the dominan...Photoinduced absorption; Photocarriers; Bipolarons; Photoexcitation1986-02
10 Vardeny, Zeev ValentinePhotoinduced absorption spectra in amorphous Si:H and Ge:H and microcrystalline Si:HThe steady state subgap photoinduced absorpotion bands in a-Ge:H and a-Si:H are interpreted in terms of two kinds of optical transitions of photoexcited carriers from traps in the gap into the bands of which one produces absorption and the other produces bleaching. The photoinduced absorption in mic...Photoinduced absorption; Si:H; Ge:H; Amorphous silicon; Amorphous germanium; Microcrystalline silicon1984
11 Vardeny, Zeev ValentinePhotoinduced absorption spectra in α-GeH and α-Si:HMeasurements of steady-state photoinduced absorption in α-Ge:H and α-Si:H were extended to cover the energy range from 0.25 to 1.9 eV. The subgap photoinduced-absorption bands in both materials are interpreted in terms of four kinds of optical transitions of photogenerated carriers from traps in ...Photoinduced absorption; in a-GeH; a-Si:H; Amorphous germanium; Amorphous silicon1984-07
12 Vardeny, Zeev ValentinePhotoinduced IR active vibrations in trans-(CD)x: a three-mode systemIn a recent Letter Blanchet et al.? have extended photoinduced absorption measurements of frYms-polyacetylene to lower energy than obtained before 2 for both isotopes, (CH)x and (CD)X. While in (CE)X three strong ir-active vibrations (IRAV) are photoinduced, only two IRAV were observed in (CD)X, at...Photoinduced absorption; IR active vibrations1983
13 Vardeny, Zeev ValentinePicosecond trapping of photocarriers in amorphous siliconTrapping of photoexcited carriers in the picosecond and subnanosecond time domains was studied by measuring the decay of photoinduced absorption (PA) in a-Si, a-Si:F, a-Si:H, and a-Si:H:F. We found that when the midgap density of states decreases, both the trapping time and its temperature dependenc...Photocarriers; Amorphous silicon; Picosecond trapping; Photoinduced absorption1983
14 Vardeny, Zeev ValentineRecombination kinetics in ?-Si:HMort et al.1 reinterpreted our data on the relaxation of photoinduced absorption (PA) in a-Si:H. 2 We want to show that the proposed interpretation contradicts one basic feature of the data while our original interpretation is in good agreement with experiment.Hydrogenated amorphous silicon; a-Si:H; Recombination kinetics; Photoinduced absorption; Decay; Relaxation1981
15 Vardeny, Zeev ValentineRelaxation of photoinduced sub-bandgap absorption in a-Si:HThe decay of photoinduced sub-bandgap absorption (PA) following pulsed excitation was studied in the temperature range 80 - 305K, in a-Si:H samples prepared by glow discharge and sputtering. The decay was interpreted in terms of bimolecular diffusion limited recombination involving dispersive trans...Photoinduced absorption; Sub-bandgap absorption; Glow discharge; Sputtering; Decay1981
16 Vardeny, Zeev ValentineSpin and spectral signatures of polaron pairs in π-conjugated polymersWe have studied polaron pair photoexcitations in a variety of π-conjugated polymer films by photoinduced absorption (PA) and optically-detected magnetic resonance (ODMR). An exchange interaction between polarons broadens the ODMR spectrum, permitting the unambiguous identification of the polaron pa...Polaron pair; ODMR; Photoinduced absorption; Spin signatures; Spectral signatures; pi-conjugated polymers1997
17 Vardeny, Zeev ValentineSpin and spectral signatures of polaron pairs in ∏-conjugated polymersWe have studied polaron pair photoexcitations in a variety of p-conjugated polymer films by photoinduced absorption (PA) and optically detected magnetic resonance (ODMR). Both luminescent and nonluminescent polymers have been studied. An exchange interaction between polarons broadens their magneti...Spin signatures; spectral signatures; Photoinduced absorption; Photoexcitation1997-08
18 Vardeny, Zeev ValentineSpin dependent photoinduced absorption in a-Si:HWe have studied photoexcitation dynamics in undoped a-Si:H from 80 K to 300 K by the techniques of photoluminescence (PL), photoinduced absorption (PA) and their respective versions of optically detected magnetic resonance, namely PLDMR and PADMR. Both PL and PA spectra are composed of low and high ...a-Si:H; Amorphous silicon; Spin dependent; Photoinduced absorption1997
19 Vardeny, Zeev ValentineSpin-dependent delayed luminescence from nongeminate pairs of polarons in ∏-conjugated polymersWe measured cw photoinduced absorption (PA) and spin- 1 2 PA- and photoluminescence detected magnetic resonance (PADMR and PLDMR, respectively) in films of two representative p-conjugated polymers; poly(phenylene-vinylene) and polythiophene. From the dependences of the polaron PA and PLDMR on the ...pi-conjugated polymers; Nongeminate pairs; Spin-dependent delayed luminescence; Photoinduced absorption; Poly(phenylene-vinylene)2002-12
20 Vardeny, Zeev ValentineTime resolved spectroscopy of photoinduced absorption in glow-discharge a-Si:HThe time and temperature dependence of the photoinduced absorption spectra was measured in glow-discharge a-Si:H in the energy range 0.7 to 1.4 eV, temperature interval 10 to 306K and time domain 2 ys to 2 ms. The results are consistent with a model based on thermalization of excess carriers in tra...Photoinduced absorption; Glow-discharge a-Si:H; Thermalization; Excess carriers; Trap states; Time dependence; Temperature dependence1981-10
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