OH megamaser的抽运效率

到目前为止已发现了106个OH megamaser源。经典的OH megamaser模型给出宿主星系的强的远红外辐射抽运非饱和的OH megamaser。抽运效率(S1667/S60)对于非饱和OH megamaser及其宿主星系来说是一个重要的物理参数。研究了什么物理量与抽运效率有关,得到无论OH megam aser的光度还是OH megamaser 1667MHz的流量密度都与抽运效率相关。但是主线强度比,主线 1667MHz的光学深度绝对值,主线1665MHz的流量密度均与抽运效率不相关。     

OH气辉对重力波响应的模式研究

重力波是中间层大气的重要能量来源,气辉观测为研究中间层重力波特性提供了极好的方法。本文利用最新的 OH 气辉激发机制,建立了一个较完整的光化、动力模式来分析重力波传播对 OH 气辉的影响。结果表明,化学反应速率系数不定性对 Krassovsky 比振幅的影响较小,但淬灭过程的影响必须考虑。Krassovsky 比的振幅和相位均依赖于波周期,其振幅在2.1和10.3之间变化;这表明 OH 气辉亮度的相对变化大于温度的相对变化。一般情况下,重力波引起的温度扰动超前于气辉亮度的变化。与实测资料比较发现,两者变化趋势基本一致,在短周期波时吻合较好。     

Discovery of large-scale methanol and hydroxyl maser filaments in W3(OH)

Images of the 6.7-GHz methanol maser emission from W3(OH) made at 50- and 100-mas angular resolution with the Multi-Element Radio-Linked Interferometer Network (MERLIN) are presented. The masers lie across the western face of the ultracompact H  ii region in extended filaments which may trace large-scale shocks. There is a complex interrelation between the 6.7-GHz methanol masers and hydroxyl (OH) masers at 1.7 and 4.7 GHz. Together the two species trace an extended filamentary structure that stretches at least 3100 au across the face of the ultracompact H  ii region. The dominant 6.7-GHz methanol emission coincides with the radio continuum peak and is populated by masers with broad spectral lines. The 6.7-GHz methanol emission is elongated at position angle 50° with a strong velocity gradient, and bears many similarities to the methanol maser disc structure reported in NGC 7538. It is surrounded by arcs of ground state OH masers at 1.7 GHz and highly excited OH masers at 13.44 GHz, some of which have the brightest methanol masers at their focus. We suggest that this region hosts the excitation centre for the ultracompact H  ii region.     

河外星系ⅢZw35的OH megamaser辐射谱的研究

我们用ⅢＺｗ３５的流量密度函数，来拟合观测得到的ＯＨｍｅｇａｍａｓｅｒ辐射谱。ＯＨｍｅｇａｍａｓｅｒ斑点处在窄线区薄盘上，作旋转运动和径向膨胀运动。窄线区薄盘是侧向的。从理论上我们得到ＯＨｍｅｇａｍａｓｅｒ辐射流量密度．发现与其辐射谱中主峰和伴峰相对应的ＯＨｍｅｇａｍａｓｅｒ斑点处在窄线区薄盘的不同位置。     

河外星系OH超脉泽的观测和研究

自从首次发现河外星系OH超脉泽以来，30多年(特别是近10年)中对河外星系OH超脉泽的观测和研究取得了极大的进展。到目前为止已发现106个河外星系OH超脉泽，其中包括59个较高红移的源。对河外星系OH超脉泽的观测和研究，是探测和研究其所成协的活动星系核、星暴星系的中央源和拱核盘的有效工具。主要评述对河外星系OH超脉泽的搜索、观测和理论研究现状。     

Hydroxyl airglow on Venus in comparison with Earth

Hydroxyl nightglow is intensively studied in the Earth atmosphere, due to its coupling to the ozone cycle. Recently, it was detected for the first time also in the Venus atmosphere, thanks to the VIRTIS-Venus Express observations. The main Δν=1, 2 emissions in the infrared spectral range, centred, respectively, at 2.81 and 1.46 μm (which correspond to the (1-0) and (2-0) transitions, respectively), were observed in limb geometry (Piccioni et al., 2008) with a mean emission rate of 880±90 and 100±40 kR (1R=10⁶ photon cm⁻² s⁻¹ (4πster)⁻¹), respectively, integrated along the line of sight. In this investigation, the Bates-Nicolet chemical reaction is reported to be the most probable mechanism for OH production on Venus, as in the case of Earth, but HO₂ and O may still be not negligible as mechanism of production for OH, differently than Earth. The nightglow emission from OH provides a method to quantify O₃, HO₂, H and O, and to infer the mechanism of transport of the key species involved in the production. Very recently, an ozone layer was detected in the upper atmosphere of Venus by the SPICAV (Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus) instrument onboard Venus Express (Montmessin et al., 2009); this discovery enhances the importance of ozone to the OH production in the upper atmosphere of Venus through the Bates-Nicolet mechanism. On Venus, OH airglow is observed only in the night side and no evidence has been found whether a similar emission exists also in the day side. On Mars it is expected to exist both on the day and night sides of the planet, because of the presence of ozone, though OH airglow has not yet been detected.In this paper, we review and compare the OH nightglow on Venus and Earth. The case of Mars is also briefly discussed for the sake of completeness. Similarities from a chemical and a dynamical point of view are listed, though visible OH emissions on Earth and IR OH emissions on Venus are compared.     

全球二维大气化学模式和大气化学成分的数值模拟

建立了一个全球二维纬向平均化学模式,模式包括了从90°S到90°N,从地面到20 km高度的大气.模式中应用的流场来自根据加热率计算得到的剩余环流.模式化学部分包括34种大气成分、104个化学反应和光化学反应.其中,甲烷、一氧化碳和氮氧化物排放分为季节性和非季节性排放源,并将其参数化为时间和纬度的函数再应用到模式中去.按1990年的甲烷、一氧化碳和氮氧化物的的排放水平模拟得到了多种大气组成的分布,模拟结果与观测有较好的一致性.由于模式考虑了一氧化碳的季节变化,模拟得到的OH自由基分布更为合理.模式的建立为今后进一步研究大气微量成分的全球循环过程及其长期变化提供了有效的手段.     

Formulation and Evaluation of IMS, an Interactive Three-Dimensional Tropospheric Chemical Transport Model 3. Comparison of Modelled C2–C5 Hydrocarbons with Surface Measurements

In part 3 of this series of papers on a new 3-D global troposphericchemical transport model, using an Integrated Modelling System (IMS), anevaluation of the model performance in simulating global distributions andseasonal variations for volatile organic compounds (VOCs) in the atmosphere,is presented. Comparisons of model OH concentrations with previous modelstudies show consistent modelled OH levels from the subtropics tomidlatitudes, while more discrepancies occur over the tropical lowlatitudes, with IMS predicting the highest levels of OH. The close agreementbetween modelled OH concentrations over midlatitudes, where high surfaceNO_xand VOC concentrations are also found, is indicative of the strongphotochemical coupling between NO_x, VOCs and O₃ overthese latitudes. IMSOH concentrations in the Northern Hemisphere (NH) midlatitudes during summerare generally lower than available measurements, implying that models ingeneral are underestimating OH levels at this location and time of year.Substantial differences between model OH concentrations over low latitudesclearly highlight areas of uncertainty between models. IMS OH concentrationsare the highest in general of the models compared, one possible reason isthat biogenic emissions of species such as isoprene and monoterpenes arehighest in IMS, leading to higher O₃ levels and hence higher OH.Generally, the IMS VOC concentrations show a similar seasonality to themeasurements at most locations. In general though, IMS tends to underestimatethe NH wintertime VOC maximum and overestimate the NH summertime VOCminimum. Such an overestimate in summer could be due to IMSunderestimating OH levels, or an overestimation of VOC emissions or possiblya problem with model transport, all of these possibilities are explored.Except for n-pentane, the model underprediction of a VOC maximum during theNH winter month strongly suggests a missing emission mechanism in the modelor an underestimate of an existing one. It is very likely that there is alack of time varying emission sources in the model to account for theseasonal change in emission behaviour such as increasing energy usage (e.g.,electricity and gas), road transportation, engine performance, and otheranthropogenic factors which show strong seasonal characteristics. Theanomalous overprediction of wintertime n-pentane compared with its closesummertime prediction with the measurements suggest that emissions in thiscase may be too high.     

OH气辉对重力波响应的模式研究

重力波是中间层大气的重要能量来源,气辉观测为研究中间层重力波特性提供了极好的方法。本文利用最新的 OH 气辉激发机制,建立了一个较完整的光化、动力模式来分析重力波传播对 OH 气辉的影响。结果表明,化学反应速率系数不定性对 Krassovsky 比振幅的影响较小,但淬灭过程的影响必须考虑。Krassovsky 比的振幅和相位均依赖于波周期,其振幅在2.1和10.3之间变化;这表明 OH 气辉亮度的相对变化大于温度的相对变化。一般情况下,重力波引起的温度扰动超前于气辉亮度的变化。与实测资料比较发现,两者变化趋势基本一致,在短周期波时吻合较好。     

Products and Kinetics of the OH‐radical‐induced Dealkylation of Atrazine

Hydroxyl radicals, generated radiolytically in N₂O/O₂‐saturated solutions, yield in their reaction with atrazine equal amounts of deethylatrazine and acetaldehyde (40% of OH radical yield) and deisopropylatrazine and acetone (16%), respectively. The precursors of deethylatrazine and acetaldehyde is their Schiff base which hydrolyzes slowly (OH^–‐catalyzed: k = 5.2 dm³ mol^–1 s^–1). The hydrolysis of the Schiff base of deisopropylatrazine and acetone is too fast to be detected. In a pulse radiolysis experiment, the intermediate formed upon OH‐radical attack (k = 3·10⁹ dm³ mol^–1 s^–1) has a strong absorption at 440 nm. It decays in the presence of oxygen (k = 1.3·10⁹ dm³ mol^–1 s^–1), and upon deprotonation [pK_a(peroxyl radicals) ≈ 10.5] the peroxyl radicals thus‐formed eliminate superoxide radicals (k = 2.9·10⁵ s^–1). s‐Triazine itself reacts much more slowly with OH radicals (k = 9.7·10⁷ dm³ mol^–1 s^–1). This can explain, why in the case of atrazine in comparison to other aromatic compounds, e.g. toluene, the addition of the OH radical to the ring (estimated at ca. 40%) is of relatively little importance as compared to an H‐abstraction from (activated) positions of the side groups.