共查询到20条相似文献，搜索用时 531 毫秒
1.
Huang X McCoy AB Bowman JM Johnson LM Savage C Dong F Nesbitt DJ 《Science (New York, N.Y.)》2006,311(5757):60-63
We present two quantum calculations of the infrared spectrum of protonated methane (CH5+) using full-dimensional, ab initio-based potential energy and dipole moment surfaces. The calculated spectra compare well with a low-resolution experimental spectrum except below 1000 cm(-1), where the experimental spectrum shows no absorption. The present calculations find substantial absorption features below 1000 cm(-1), in qualitative agreement with earlier classical calculations of the spectrum. The major spectral bands are analyzed in terms of the molecular motions. Of particular interest is an intense feature at 200 cm(-1), which is due to an isomerization mode that connects two equivalent minima. Very recent high-resolution jet-cooled spectra in the CH stretch region (2825 to 3050 cm(-1)) are also reported, and assignments of the band origins are made, based on the present quantum calculations. 相似文献
2.
Polyansky OL Császár AG Shirin SV Zobov NF Barletta P Tennyson J Schwenke DW Knowles PJ 《Science (New York, N.Y.)》2003,299(5606):539-542
The spectrum of water vapor is of fundamental importance for a variety of processes, including the absorption and retention of sunlight in Earth's atmosphere. Therefore, there has long been an urgent need for a robust and accurate predictive model for this spectrum. In our work on the high-resolution spectrum of water, we report first-principles calculations that approach experimental accuracy. To achieve this, we performed exceptionally large electronic structure calculations and considered a variety of effects, including quantum electrodynamics, which have routinely been neglected in studies of small many-electron molecules. The high accuracy of the resulting ab initio procedure is demonstrated for the main isotopomers of water. 相似文献
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纳米材料对水团簇的影响 总被引：1，自引：0，他引：1
[目的]为纳米材料在生物领域的应用提供依据。[方法]通过紫外吸收光谱和核磁共振图谱研究纳米材料处理水分子团簇的变化。[结果]在190~325 nm波段,纳米材料处理水的紫外吸收光谱的光吸收增强,表明水分子的结构和能态发生了变化;水的17O-NMR半峰宽变窄,化学位移减小,向低场移动。[结论]水经纳米材料处理后分子团变小,活性提高。 相似文献
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Schenkl S van Mourik F van der Zwan G Haacke S Chergui M 《Science (New York, N.Y.)》2005,309(5736):917-920
The ultrafast evolution of the electric field within bacteriorhodopsin was measured by monitoring the absorption changes of a tryptophan residue after excitation of retinal. The Trp absorption decreases within the first 200 femtoseconds and then recovers on time scales typical for retinal isomerization and vibrational relaxation. A model of excitonic coupling between retinal and tryptophans shows that the signal reflects a gradual rise of the retinal difference dipole moment, which precedes and probably drives isomerization. The results suggest an intimate connection between the progressive dipole moment change and the retinal skeletal changes reported over the same time scale. 相似文献
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采用热重-红外光谱分析联用技术分析森林可燃物气体排放的规律,测定气体的红外吸收频谱,对气体成分进行定性和定量分析。以朗伯特-比尔（Lambert—Beer）定律为理论基础,通过定量分析可燃物气体的红外光谱,精确地测定了森林可燃物热失重的过程与CO2气体排放量的相关性,以福州地区马尾松林下地衰可燃物为研究对象,估算了不同林型的马尾松林下地表可燃物的CO2释放量。 相似文献
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The spectral reflectivity (0.30 to 1.10 microns) of several asteroids has been measured for the first time. The reflection spectrum for Vesta contains a strong absorption band centered near 0.9 micron and a weaker absorption feature between 0.5 and 0.6 micron. The reflectivity decreases strongly in the ultraviolet. The reflection spectrum for the asteroid Pallas and probably for Ceres does not contain the 0.9-micron band. Vesta shows the strongest and best-defined absorption bands yet seen in the reflection spectrum for the solid surface of an object in the solar system. The strong 0.9-micron band arises from electronic absorptions in ferrous iron on the M2 site of a magnesian pyroxene. Comparison with laboratory measurements on meteorites and Apollo 11 samples indicates that the surface of Vesta has a composition very similar to that of certain basaltic achondrites. 相似文献
8.
北京密云油松人工林林冠降水截留特征研究 总被引：1，自引：1，他引：1
该文对密云水库集水区油松人工林林冠截留的规律进行了研究,尝试用合适的统计模型和概念模型描述单场降雨下林冠截留量与降水量的关系.通过在油松试验地外测定大气降雨量,在林内测定穿透雨量和树干茎流量,得出了在不同降雨量和降雨强度下的林冠截留量.结果显示:以S型曲线作为统计模型能很好地模拟降雨量与截留量的关系;比较简单的概念模型的模拟效果最好,其中的降雨蒸发率α和林冠吸附降雨容量Im的参考数值分别为0.025和3.297 mm;把降雨强度加入半理论模型,可以得出截流量与降雨强度成负相关关系. 相似文献
9.
A Arking 《Science (New York, N.Y.)》1996,273(5276):779-782
An atmospheric general circulation model, which assimilates data from daily observations of temperature, humidity, wind, and sea-level air pressure, was compared with a set of observations that combines satellite and ground-based measurements of solar flux. The comparison reveals that the model underestimates by 25 to 30 watts per square meter the amount of solar energy absorbed by Earth's atmosphere. Contrary to some recent reports, clouds have little or no overall effect on atmospheric absorption, a consistent feature of both the observations and the model. Of several variables considered, water vapor appears to be the dominant influence on atmospheric absorption. 相似文献
10.
Vaska L 《Science (New York, N.Y.)》1966,152(3723):769-771
Chlorocarbonyl-bis(triphenylphosphine)iridium(I), in solution, reacts reversibly with carbon monoxide under normal conditions, one molecule per metal atom. Formation of a 1 : 1 metal complex-CO adduct is verified by CO absorption measurements and the infrared spectrum of the adduct measured in situ. The spectrum suggests that the metal-C-O bonding is of the type found in conventional metal carbonyl. 相似文献
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In this report the fluxes measured by the solar flux radiometer (LSFR) of the Pioneer Venus large probe are compared with calculations for model atmospheres. If the large particles of the middle and lower clouds are assumed to be sulfur, strong, short-wavelength absorption results in a net flux profile significantly different from the LSFR net flux measurements. Models in which the smallest particles are assumed to be sulfur gave flux profiles consistent with the measurements if an additional source of absorption is included in the upper cloud. The narrowband data from 0.590 to 0.665 micrometer indicate an absorption optical depth of about 0.05 below the cloud bottom. The broadband data imply that either this absorption extends over a considerable wavelength interval (as might be the case for dust) or that a very strong absorption band lies on one side of the narrowband filter (as suggested by early Venera 11 and Venera 12 reports). Thermal balance calculations based on the measured visible fluxes indicate high surface temperature for reasonable assumptions of cloud opacity and water vapor abundance. The lapse rate becomes convective within the middle cloud. For water mixing ratios of 2.0 x 10(-4) below the clouds we find a subadiabatic region extending from the cloud bottom to altitudes near 35 kilometers. 相似文献
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冬小麦拔节期冠层晴天光谱特征分析 总被引：2，自引：0，他引：2
利用美国ＳＥ５９０辐射分光光谱仪对晴天中午冬小麦冠层各种辐射光谱成分进行了测定研究,给出了冠层上方总辐射、反射辐射及基部透射辐射的各种光谱变化规律,研究表明冠层上方总辐射、反射辐射、基部透射辐射及吸收辐射中光合有效辐射所占百分比分别为４７９％、１６２％、２１６％和７３９％。在此基础上,进一步给出了小麦冠层反射率光谱变化规律,并利用三次样条函数对冬小麦冠层反射率光谱曲线进行模拟,结果表明２５６组实测数据组成的反射率—波长曲线可以由１２组实测数据通过三次样条函数进行较为准确的模拟,平均模拟误差为４７％,从而为冬小麦反射率光谱曲线数据压缩,建立作物遥感数据库提供了一种理论方法。 相似文献
14.
袁浩 《北京林业大学学报》1988,10(1):92-96
氨三乙酸—铵盐镀锌废水通过化学凝聚、活性碳静电吸附等流程处理,可使其得到净化。经原子吸收光谱分析表明:利用此流程除锌效率可达到95％以上,经过处理的水含锌量符合国家环境保护条例的标准。而且可以回收氯化锌和循环使用净化水,活性碳也不用另行再生。 相似文献
15.
袁浩 《北京林业大学学报》1988,(1)
氨三乙酸—铵盐镀锌废水通过化学凝聚、活性碳静电吸附等流程处理,可使其得到净化。经原子吸收光谱分析表明:利用此流程除锌效率可达到95％以上,经过处理的水含锌量符合国家环境保护条例的标准。而且可以回收氯化锌和循环使用净化水,活性碳也不用另行再生。 相似文献
16.
The radiative signature of upper tropospheric moistening 总被引：1，自引：0，他引：1
Soden BJ Jackson DL Ramaswamy V Schwarzkopf MD Huang X 《Science (New York, N.Y.)》2005,310(5749):841-844
Climate models predict that the concentration of water vapor in the upper troposphere could double by the end of the century as a result of increases in greenhouse gases. Such moistening plays a key role in amplifying the rate at which the climate warms in response to anthropogenic activities, but has been difficult to detect because of deficiencies in conventional observing systems. We use satellite measurements to highlight a distinct radiative signature of upper tropospheric moistening over the period 1982 to 2004. The observed moistening is accurately captured by climate model simulations and lends further credence to model projections of future global warming. 相似文献
17.
Lake Superior was chosen as an experimental site to compare sound absorption of freshwater with the results of absorption measurements in seawater. The relaxation-like absorption at 1 kilohertz occurring in seawater is also present in freshwater. A relaxation related to the structural characteristics rather than to the salt content of water may be responsible for the anomalous absorption. 相似文献
18.
Intracellular absorption difference spectrum of Limulus extra-ocular photolabile pigment 总被引：7，自引：0，他引：7
G C Murray 《Science (New York, N.Y.)》1966,154(753):1182-1183
Microspectrophotometric measurements on single cell bodies located on the surface of the"lateral olfactory nerve" of Limulus polyphemus show they contain a photolabile pigment with a absorption-difference spectrum similar in shape to that of most other visual pigments and with a maximum absorption at 529 +/- 5 nanometers. 相似文献
19.
Earth's magnetic field has decayed by about 5% per century since measurements began in 1840. Directional measurements predate those of intensity by more than 250 years, and we combined the global model of directions with paleomagnetic intensity measurements to estimate the fall in strength for this earlier period (1590 to 1840 A.D.). We found that magnetic field strength was nearly constant throughout this time, in contrast to the later period. Extrapolating to the core surface showed that the fall in strength originated in patches of reverse magnetic flux in the Southern Hemisphere. These patches were detectable by directional data alone; the pre-1840 model showed little or no evidence of them, supporting the conclusion of a steady dipole up to 1840. 相似文献
20.
Strong photoinduced nucleation of pure water vapor was found to occur in a wavelength range where no ultraviolet absorption of water vapor has been reported. Systematic studies were made of the dependence of the nucleation rate and the delay time for the initiation of nucleation on light intensity. The results obtained were accurately fitted by a phenomenological mechanism whereby the nucleation is initiated by clusters accumulating an appropriate number of photoexcited water molecules. 相似文献