Preparation and X-ray crystal structure analysis of 1,6-dinitrocycloheptatriene

Burnett, Ian J.; Conole, Gràinne; O'Donovan, G; Shepherd, Michael K.

doi:10.1039/c39940001187

Cited by 2 publications

(1 citation statement)

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“…116 On the other hand, the reaction of cycloheptatriene with copper nitrate in Ac 2 O gives the 1-nitro derivative 128 in low yield. 117 The role of copper ions is probably to inhibit the oxidation process. Subsequent nitration of the mononitro derivative 128 with acetyl nitrate gave the dinitro compound 129.…”

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confidence: 99%

Reactions of alkenes with nitrogen oxides and other nitrosating and nitrating reagents

Степанов¹,

Veselovsky²

2003

Russ. Chem. Rev.

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We present a theory of light amplification in a cavity based on irreversibility of coherent excitation. It is predicted that the irreversibility of coherent excitation leads to a new way of lasing which is different from lasing with and without inversion in the conventional sense. Lasing with dynamically induced inversion is possible in coherently driven systems in which there is no conventional source of irreversible population pumping. This laser displays two interesting and important features: the maximum gain with inversion is substantially greater than gain without inversion, and in spite of the presence of the inversion, the noise intensity is reduced below the shot-noise limit.As is well known, atomic transitions arise in two ways: they can occur spontaneously as a consequence of the atom's coupling to the vacuum, or they can be stimulated by external perturbation such as a laser field. Usually, the spontaneous transition is referred to as spontaneous emission, spontaneous decay, etc, while the stimulated transition is known as coherent excitation, coherent driving, coherent coupling, etc. The spontaneous transitions are irreversible since they occur from states of higher energy to states of lower energy. The stimulated transitions, however, are reversible, i.e. the probabilities of photon absorption and emission are equal. As a result, it is impossible to achieve steady-state population inversion in a driven two-level atom. It is a widely held view that, in order to create the population inversion required to achieve light amplification, one has to utilize the irreversible transition as a population pump in a multilevel system.Recently, the new concept of lasing without inversion has received much attention (see [1] for reviews). It has been shown that, in cases where it is difficult or even impossible to create the required population inversion via conventional pumping, lasing without inversion provides an important and interesting alternative. It is identified that the origin of the inversionless gain is attributed to either inversion between dressed states or coherence among these states [2]. The inversionless gain has been demonstrated [3] and the first lasers without inversion have been realized [4]. In addition, dressed-state lasers belong to the class of lasers without inversion since there is no inversion between bare atomic states. The idea stems from Mollow [5], who predicted that a strongly driven two-level atom can amplify a weak probe beam at one of the Rabi sideband frequencies. The gain is due to population inversion between dressed states [6]. As will be shown, however, lasing without inversion is not the only option when it is difficult or impossible to provide the required population inversion using conventional pumping.In this letter, we will present a theoretical analysis of light amplification in a cavity, based on irreversibility of coherent excitation. It is predicted that lasing with inversion is possible 0953-4075/00/070265+10$30.00

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confidence: 99%