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The authors report on midinfrared photoreflectance measurements of the band gap ͑E 0 ͒ and spin-orbit splitting energies ͑⌬ 0 ͒ in InAs-rich InAsSb and GaInAsPSb samples for varying antimony contents ഛ22.5%. The E 0 behavior as a function of Sb content is consistent with the literature value bowing parameter of ϳ670 meV. However, ⌬ 0 does not exhibit the positive bowing of +1170 meV quoted in the literature: rather, a best fit to their data tentatively suggests a negative bowing of −225 meV. This result is likely to have strong impact due to the importance of the ⌬ 0 parameter in governing InAsSb-based device performance. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2728752͔ Recent interest in developing midinfrared ͑MIR, 2-5 m͒ light emitters and detectors has been driven by the wide range of potential applications in this spectral region. 1As a result of high Auger recombination coefficients, MIR semiconductors exhibit low quantum efficiencies and devices often have to operate below room temperature.2 The Auger recombination rates are sensitive to the fundamental band gap energy E 0 and ͓in the case of the conduction, heavy-hole, spin split-off hole, heavy-hole ͑CHSH͒ process͔ the spinorbit splitting energy ⌬ 0 .3 Therefore, in order to evaluate losses by these nonradiative recombination paths, a good knowledge of both E 0 and ⌬ 0 is essential.The InAs 1−x Sb x alloy plays a particularly important role in many MIR devices. 2,4,5 As a ternary alloy it is possible to define the compositional dependence of a parameter T ͑such as E 0 or ⌬ 0 ͒ using T = xB 1 + ͑1−x͒B 2 − x͑1−x͒C, where B 1 is the binary end-point InSb value, B 2 the InAs value, and C a bowing parameter which describes any deviation from the virtual crystal approximation. 6 A range of studies of E 0 in InAs 1−x Sb x indicates that C lies between 570-690 meV [7][8][9] and the review of Vurgaftman et al. recommends using C͑E 0 ͒ = + 670 meV. 10

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Photochemical study of the zinc cis 3 (4 imidazolylphenyl) 1 (pyridin 2 yl)[60]fullereno[1,2 с]pyrrolidinemeso tetraphenylporphyrinate dyadAxial coordination of fullerenopyrrolidine bearing the donor imidazolyl group, cis 3 (4 imidazolylphenyl) 1 (pyridin 2 yl)[60]fullereno[1,2 c]pyrrolidine (С 60 ∼Im), with zinc meso tetraphenylporphyrinate (ZnTPP) in an o dichlorobenzene solution affords a non covalently bonded donor acceptor dyad ZnTPP-С 60 ∼Im. The photochemical behavior of the ZnTPP-С 60 ∼Im complex was studied by fluorescence (excitation at λ = 420 nm) and laser kinetic spectroscopy (excitation at λ = 532 nm, 12 ns). The formation constant of the 1 : 1 porphyrin-fullerenopyrrolidine complex determined from quenching of ZnTPP fluorescence assuming static intracomplex quenching is 1.6•10 4 L mol -1 . Absorption spectra of the excited states in the system consisting of ZnTPP and Im∼C 60 (ZnTPP/C 60 ∼Im) were measured in solution from 380 to 1000 nm. The quenching constant of the triplet excited ZnTPP with fullerenopyrrolidine С 60 ∼Im was determined. The results obtained indicate the formation of the triplet exciplex {PL}* {P δ+ ···L δ-} in the ZnTPP/C 60 ∼Im system upon laser pho tolysis.