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We have studied the temperature dependence of optical transitions in dilute GaAsN alloys using photoreflectance (PR). A delocalized‐state transition is clearly observed in PR spectra while several localized‐state emission lines due to isoelectronic centers appear in photoluminescence spectra. The energy of optical transitions observed in PR spectra is in agreement with the excitonic transition energy in photoluminescence excitation spectra, clearly showing that the optical transitions in PR spectra are excitonic transitions. We analyzed the temperature dependence of the excitonic transition energies using the Bose–Einstein statistical expression, and found that even dilute alloys follow the same trend as GaAsN alloys with higher nitrogen concentrations. We discuss the coexistence of localized and delocalized states in dilute GaAsN alloys in terms of the random distribution of N atoms.

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Traditional grammars of Persian recognize two copular series for the affirmative indicative present tense, which we call the independent copulas and dependent copulas. The former has been considered as a full verb whereas the latter has been described as an enclitic. This paper explores the syntactic and phonological properties of the two copular series by looking into cases in which only one form is grammatical. We propose that the dependent copulas are not enclitics but have the same internal structure as the independent copulas, consisting of a null verbal stem and a person inflectional suffix. Through examinations of the syntactic operations of A-bar movement via association with an enclitic focus particle and ellipsis of the complement, as well as stress assignment in copular constructions, we demonstrate that nonparallel grammatical judgments arise from unsuccessful stress assignment, which results from the absence of overt material in the complement. This work contributes a new look at the copular system in Persian and beyond, which has not been extensively investigated in the literature.