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G. Di Lonardo L. Fusina A. Trombetti Ian M. Mills 《Journal of Molecular Spectroscopy》1982,92(2):298-325
The ir absorption of gaseous 15NH3 between 510 and 3040 cm?1 was recorded with a resolution of 0.06 cm?1. The ν2, 2ν2, 3ν2, ν4, and ν2 + ν4 bands were measured and analyzed on the basis of the vibration-rotation Hamiltonian developed by V. ?pirko, J. M. R. Stone, and D. Papou?ek (J. Mol. Spectrosc.60, 159–178 (1976)). A set of effective molecular parameters for the ν2 = 1, 2, 3 states was derived, which reproduced the transition frequencies within the accuracy of the experimental measurements. For ν4 and ν2 + ν4 bands the standard deviation of the calculated spectrum is about four times larger than the measurements accuracy: a similar result was found for ν4 in 14NH3 by ?. Urban et al. (J. Mol. Spectrosc.79, 455–495 (1980)). This result suggests that the present treatment takes into account only the most significant part of the rovibration interaction in the doubly degenerate vibrational states of ammonia. 相似文献
156.
Subpicosecond pulse generation has been examined in synchronously pumped mode-locked ring dye laser systems. These include hybrid and composite absorber/gain media arrangements as well as a simple synchronous cavity. The shortest pulses recorded were 0.3 ps for the hybrid system, and this has been shown to be critically dependent on the positioning of the absorber jet in the centre of the cavity to better than 50 m. Stable operation for subpicosecond pulse generation has been achieved in the ring configuration with greater wavelength tunability and higher average power conversion efficiency than with conventional cavity arrangements. 相似文献
157.
An investigation was undertaken in late 1982/early 1983 into the computing needs of operational research workers in British Gas. The approach was first to draw up a specification of O.R.'s computing needs in terms of service levels, provision of hardware and software. Alternative options for meeting this specification were then costed out. Options examined included an interactive service on the mainframe computer, use of a minicomputer, and the use of micros plus mainframe interactive service. The results are given in the paper for various sizes of O.R. group, together with the results of sensitivity exercises. 相似文献
158.
Ian J. Hodgkinson Qi h. Wu Matthew Arnold Martin W. McCall Akhlesh Lakhtakia 《Optics Communications》2002,210(3-6):201-211
A left-handed chiral sculptured thin film (STF) that reflects strongly at the wavelength of the circular Bragg resonance tends to partially convert the handedness of incident LCP (left-circularly-polarized) light to RCP (right-circularly-polarized). We show that the cross-polarized component of the reflected RCP beam can be eliminated by interference with an additional RCP beam that is reflected at the interface of an isotropic cover and an AR (antireflecting) layer. For best results the refractive index and thickness of the AR layer need to accommodate a phase change on reflection that occurs at the chiral film. Effective suppression of the reflectances RRR, RRL, RLR and the transmittances TRL, TLR can be achieved by sandwiching the chiral reflector between such amplitude and phase-matched AR coatings. Co-polarized chiral reflectors of this type may form efficient handed optical resonators. For LCP light the optical properties of such a handed resonator are formally the same as the properties of the isotropic passive or active Fabry–Perot resonators, but the handed resonator is transparent to RCP light. 相似文献
159.
A fiber Fabry-Perot interferometer (FFPI) sensor is formed with broadband (~3 nm, 3-dB bandwidth) fiber Bragg grating (FBG) mirrors. Repetitively modulating a distributed-feedback laser produces chirping that modulates the reflectance of the FFPI. Because the reflectance of the FBG mirrors varies with optical frequency, the fringes in the sensor reflectance modulation are distinguishable, making it possible to extend the sensor dynamic range versus that of a FFPI sensor with conventional wavelength-dependent mirrors. An ambient temperature is determined in the range from 25 to 170 degrees C with a resolution of 0.005 degrees C. 相似文献
160.
In his curriculum vitae, John Hawkes lists his research interestsas geometric measure theory, probability (Lévy processes),and potential theory (probabilistic). In fact, he made significantcontributions to all three areas, and there are strong relationshipsbetween them. He used both geometric measure theory and potentialtheory as tools for his study of the trajectories of particularLévy processes, but in many cases he needed to developthe tool before it was ready to be used. We will summarise hisresearch later, but first we discuss what is known of his lifehistory. 相似文献