The magnetic shielding of 3 He is studied. The complete relativistic corrections of order O͑␣ 2 ͒, leading QED corrections of order O͑␣ 3 ln ␣͒, and finite nuclear mass effects of order O͑m / m N ͒ are calculated with high numerical precision. The resulting theoretical predictions for = 59.967 43͑10͒ ϫ 10 −6 are the most accurate to date among all elements and support the use of 3 He as a NMR standard.

The subject of this paper is the derivation of expressions describing envelopes of electromagnetic fields inside a 1D photonic crystal. The presented approach is based on an effective resonator model, which treats each layer of the photonic crystal as a resonant cavity. The model is analytic and allows one to derive parameters characterizing the photonic crystal and express electric and magnetic fields as their function. It is general enough to take into account defects of the crystal or even be used for an aperiodic structure. In the end of the paper, a few results are provided for the case of a source of radiation inside a photonic crystal along with a short discussion.PACS numbers: 42.70.Qs MotivationIt has been in the late 1980s when photonic crystals have been recognized as a distinct group of materials with unique optical properties [1,2]. Their properties are associated with an optical band structure resembling the band structure of semiconductors in electronics, and therefore photonic crystals are sometimes called "semiconductors of light". Because semiconductors have played a very important role in science and technology, becoming the fundamentals of contemporary electronics, this similarity is the cause of great interest and expectations regarding photonic crystals. Indeed, photonic crystals have been used to build many optical devices -one can mention optical waveguides [3,4], filters [5], optical switches [6], LEDs with increased efficiency [7], distributed Bragg reflector (DBR) and distributed feedback (DFB) lasers [8].It is important to understand the physics of photonic crystals to develop new devices and improve already existing ones. In this paper, there is presented an effective resonator model of a 1D photonic crystal, which allows one to exam-

In this paper, the orthonormal mode set is derived from electromagnetic field distributions of a dielectric multilayer structure, which have been obtained using the effective resonator model, presented in Acta Phys. Pol. A 111, 323 (2007)

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The aim of this paper is to present the analysis of influence of defects in 1D photonic crystal (PC) on the density of states and simultaneously spontaneous emission, in both spatial and frequency domains. In our investigations we use an analytic model of 1D PC with defects. Our analysis reveals how presence of a defect causes a defect mode to appear. We show that a defect in 1D PC has local character, being negligible in regions of PC situated far from the defected elementary cell. We also analyze the effect of multiple defects, which lead to photonic band gap splitting.Comment: presented at International Workshop on Physics of Photonic Crystals and Metamaterials, Brussels, Belgium, 12-13.06.200