首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 36 毫秒
1.
Laboratory investigations of CN radical formation by photodissociation of parent molecules have suggested the possibility of observing emission lines in cometary spectra from newly formed CN radicals. These laboratory studies have shown that high initial internal excitation of CN is the rule with excitation of rotational levels N up to 70. In the collisionless environment of the cometary atmosphere this initial excitation would yield a corresponding distribution for the lowest vibrational level of the ground X2Σ+ state. Our calculations show that it is feasible with present observational techniques to detect photochemically excited lines with N ～ 30 in the 0-0 band of the violet system.  相似文献   

2.
Altitude distributions of electronically excited atoms and molecules of oxygen and nitrogen in the aurora have been obtained by means of rocket-borne wavelength scanning interference filter photometers launched from Fort Churchill, Manitoba (58.4°N, 94.1°W) on January 23, 1974. Atomic oxygen densities derived from mass spectrometer measurements obtained during the flight are used in conjunction with the volume emission rate ratio of the N2(C3Πu?B3Πg) (0-0) second positive and N2(A3Σu+, v = 1?X1Σg+) Vegard-Kaplan bands to derive a rate constant for quenching of the N2(A3Σu+, v = 1) level with O(3P) of 1.7(±0.8) × 10?11 cm3 s?1 These data, together with O den derived from the O2(b1Σg+) state nightglow emission observed during the rocket ascent, suggest that quenching of the N2(A3Σu+, v = 1) level by O2 has a significant positive temperature dependence. The processes involved in the production and loss of the N2(A3Σu+) state are considered and energy transfer from the N2(A3Σu+) state to O(3P) is found to be a significant source of the OI 5577 Å green line in this aurora at altitudes below 130 km. Emission from the NO(A2Σ+?X2Π) gamma bands was not detected, an observation which is consistent with the mass spectrometer data obtained during the flight indicating that the NO density was <108 cm3 at 110 km. On the basis of previous rocket and satellite measurements of the NO gamma bands, energy transfer from the N2(A3Σu+) state to NO(X2Π) is shown to be an insignificant source of the gamma bands in aurora. Altitude profiles of the N2(a1Πg?X1Σg+) Lyman-Birge-Hopfield band system are presented.  相似文献   

3.
It is proposed that energy transfer from excited O2 contributes to the production of O(1S) in aurora. An analysis is presented of the OI5577 Å emission in an IBC II+ aurora between 90 and 130 km. The volume emission rate of the emission at these altitudes is consistent with the production rate of O(1S) by energy transfer to O(3P) from N2 in the A3Σ2+ state and O2 in the A3Σu+, C3Δc1Σu? states, the N2A state being populated by direct electron impact excitation and B → A cascade and the excited O2 states by direct excitation. Above the peak emission altitude (~105 km), energy transfer from N2A is the predominant production mechanism for O(1S). Below it, the contribution from quenching of the O2 states becomes significant.  相似文献   

4.
Simultaneous measurements of the nightglow profiles of the O2(b1Σg+?X3Σg?) A-band, the atomic oxygen green line and the OH (8?3) Meinel band are presented. The altitude profiles are used to determine both the excitation mechanisms for the oxygen emissions and the atomic oxygen altitude distribution. It is shown that the measurements are consistent with a green line excitation through the Barth mechanism and that the molecular oxygen emission is excited through oxygen recombination and the reaction between OH1 and atomic oxygen. The derived atomic oxygen concentrations,6.2 × 1011cm?3at 98km, are consistent with the Jacchia (1971) model.  相似文献   

5.
The24MgH+ (A 1+ –X 1+) molecular lines have been identified in the photospheric spectrum. The rotational excitation temperature determined from the analysis of molecular line intensities of24MgH+ is found to be of the order of 4850 K which corresponds to the photospheric temperature of the Sun. The CNDO/2 dipole moments of24MgH+ for internuclear distance range: (1.3–2.1) Å in theX 1+ state can be approximated byM(R)=4.92+1.33R. Estimations for the spontaneous emission Einstein coefficients (A v v ) and the absorption oscillator strengths (f v v ) for the (1, 0), (2, 0), and (2, 1) transitions in theX 1+ state of the24MgH+ ion are also made.Work partially supported by the CNPq, Brasilia under contract number 30.4076/77.  相似文献   

6.
Analysis of observed spectrograms is based on comparison with synthetic spectra. The O2(b1Σ+g?X3Σ?g Atm. (1,1) band in high latitude auroras observed from the ground is found to be the strongest in the Δv = 0 sequence. It is enhanced with altitude relative to the N2 1P(2, 0)and N+2 M(2,0) bands, but the O2 Atm. (2, 2) band has an unexpected low intensity. The range of rotational temperatures of the O2 Atm. bands varies from approx. 200 to above 500 K which indicates that the altitude of the centroid of the emission region varies from about 100 km to the F-region. The highest temperature is found in the midday aurora associated with the magnetospheric cusp. Conspicuous relative variations between the intensities of N2 and O2 spectra are documented, but a satisfactory explanation of the variety is not given. Deviations of the observed O2 Atm. band intensities from the vibrational intensity distribution predicted by Franck-Condor factors indicate that the excitation of the O2 Atm. bands in aurora is not mainly due to particle impact on O2, and the contribution due to energy transfer from hot O(1D) atoms has to be found in future research.  相似文献   

7.
Improved values of the proton impact excitation cross sections at coronal energies for all the Fe+12 ground configuration (3s 23p 2) transitions are presented. These were obtained by direct computer integration of the Schroedinger equation (with the states expressed in intermediate coupling) resulting from the semi-classical Coulomb excitation theory formulation of the process. Comparison is made with previous results. The associated rate constants at coronal temperatures are given and compared with the corresponding electron impact excitation rate constants. Some cross-section values for the Fe+13 3s 23p 2 P 1/22 P 3/2 excitation are also presented.  相似文献   

8.
Aluminium monoxide (AlO) is widely known for its astrophysical significance. An analysis of the prominent lines of the (2,3;3,2;3,4;4,5;4,3;5,6;6,7) bands of the B 2Σ+?X 2Σ+ transition with those of sunspot umbral spectral lines suggests that the AlO molecule appears to be a non-negligible component of sunspot umbrae. Results of a recent (2008) rotational analysis were used to carry out the study. The effective rotational temperature determined for the above lines in the sunspot umbral spectrum is found to be of the order of 2900 K. The radiative-transition parameters that include Franck–Condon (FC) factors, r-centroids, electronic-transition moment, Einstein coefficient, absorption–band oscillator strength, and radiative lifetime have been estimated for the experimentally known vibrational levels using the Rydberg–Klein–Rees (RKR) potential.  相似文献   

9.
Extreme ultraviolet (EUV) resonance fluorescence of the (0,v″) bands of the c′41Σu+→X1Σg+ and the (1,v″) bands of the b′ 1Σu+→X1Σg+ transitions of N2 has been observed by photon excitation of N2 in the vicinity of 95.8 nm. The integrated fluorescence intensities of the c′4→X (0,v″) emission become saturated at N2 pressures higher than ∼0.16 mTorr. The emission features in the spectral region between 105 and 130 nm become progressively significant as the N2 pressure is increased. The (1,v″) progression for v″ up to 11 of the b′→X transition and two progressions of the Lyman-Birge-Hopfield (LBH) system have been identified. The multiple scattering processes apparently cause significant reduction in the c′4→X (0,0) emission rates. The present results may be useful in the explanation of the weak c′4→X (0,0) fluorescence as well as the significant c′4→X (0,v″) features in the dayglow of the Earth observed by the Far Ultraviolet Spectroscopic Explorer.  相似文献   

10.
Recently, modelers have expressed a concern that the currently known chemistry of atmospheric NOy is deficient. It is therefore necessary to explore possible sources and sinks of atmospheric NOx that may have been overlooked. In this context, it is noteworthy that the experimentally observed, four-center, Woodward-Hoffman forbidden, reaction 02(B 3Σ) + N2 → NO(X) + NO (X) is atmospherically significant. In the 20 to 30 km region NOx production from this reaction may potentially exceed the production from the “classical” N20 + O(1D) reaction, and may provide a new mechanism to couple the solar UV variability and stratospheric ozone. The avoidance of the non-conservation of the orbital symmetry via the production of one NO in the excited electronic state being endothermic, it appears that the interaction of 02(B 3Σ) with the adjoining 1Λ, 3Λ and 3Σu+ states might be responsible for the reaction. Experimental studies of the reaction as a function of the vibrational levels of the B-state, temperature and pressure are needed for reliable atmospheric applications of this reaction. At altitudes greater than about 50 km the production of NO from 02(B) begins to decrease rapidly. The NO production from 02 (A 3Σ++) + N2 → NO + NO reaction may become important here, if the reaction is confirmed by experiments. These new sources of NOx call for new sinks of this species. In the upper stratosphere and mesosphere the chemical acceleration of NO dissociation via the reactions of electronically and vibrationally excited NO with 02 may help. In the lower atmosphere there is a possibility of the annihilation of NO, N02pair leading to the recreation of a stable NN bond. This might happen if N203 from NO and N02 recombination may photodissociate as N20 + 02. Unfortunately the requirements are stringent, and only experiments can tell whether or not this mechanism operates in the atmosphere.  相似文献   

11.
It is proposed that the available measurements of the O2(b1Σg+ ?X3Σg?) atmospheric bands both in the nightglow and in the laboratory indicate that the excitation mechanism is a two-step process rather than the direct three body recombination of atomic oxygen. It is shown that such a two-step mechanism can explain observations of the atmospheric bands both in altitude and intensity.  相似文献   

12.
A principally new, quantitative system of the classification of the spectra of planetary nebulae is proposed. Spectral class of excitation class of the nebulap is determined according to the relative intensities of emission lines (N 1+N 2) [OIII]/4686 HeII and (N 1+N 2) [OIII]/H (Table I, Figure 1). The excitation classes are obtained for 142 planetary nebulae of all classes—low (p=1–3), middle (p=4–8), and high (p=9–12+) (Tables II, III, and IV). An empirical relationship between excitation classp and mean radius of nebulae is discovered (Figure 2). This relationship as well as excitation classp, as an independend parameter, admit an evolutionary interpretation. It is shown that after reaching the highest class of excitationp=12+ the nebulae decrease their class of excitation with the further increases of sizes. The diagram of this relationship has two nearly-symmetric branches — rising and descending with the apogee onp=12+ (Figure 2).  相似文献   

13.
A recent assessment by Rees (1984) of the contribution made to the excitation of O(1S) in the aurora by the reaction of N2(A3Σ+) with O(3P) is re-examined. It is demonstrated that the contribution attributed to this reaction may have been seriously under-estimated and it is shown that the results of recent laboratory investigations do not preclude this reaction as a major source of O(1s) in the aurora.  相似文献   

14.
The spectroscopic observations of comet C/2009 R1 (McNaught) were carried out with the 2 m Zeiss-RCC Telescope of Pik Terskol Observatory operated by the International Center for Astronomical and Medico-Ecological Research (Ukraine, Russia). The Multi Mode Cassegrain spectrometer was used to obtain spectra of moderate spectral resolving power with a wavelength coverage from 4140 to 5240 Å. The spectrum is characterized by the extremely low continuum level and strong molecular features. 192 emission lines of C2, CN, CH, NH2, CO+, and CH+ have been identified by the comparison of the observed and theoretical spectra of the molecules. The ratios of the gas production rates of Q(C2)/Q(CN)=1.32, Q(CH)/Q(CN)=0.49, and Q(NH2)/Q(CN)=0.81 were derived using a Haser model.  相似文献   

15.
M.G. Heaps  J.N. Bass  A.E.S. Green 《Icarus》1973,20(3):297-303
The planet Jupiter, like the Earth, possesses a magnetic field, and, therefore, auroral activity is very likely. In this work, the auroral emissions due to electron precipitation are estimated for a model atmosphere with and without helium. The incident primary electrons, which are characterized by representative spectra, are degraded in energy by applying the continuous slow down approximation. All secondaries, tertiaries, and higher generation electrons are assumed to be absorbed locally. A compilation of excitation, dissociation, and ionization cross section data for H, H2, and He are used to model all aspects of the energy deposition process. Volume emission rates are calculated from the total direct excitation rates, and appropriate corrections for cascading are applied. Integrated column intensities of several kiloRayleighs are obtained for the various vibrational levels of the Lyman and Werner bands of H2, as well as the triplet continuum a3Σg+ → b3Σu+. Helium emissions are relatively small because the majority of electrons are absorbed above the region of maximum He concentration. Atomic hydrogen emissions are due mainly to dissociative excitation of molecular hydrogen rather than direct excitation.  相似文献   

16.
We report on ab initio coupled-cluster calculations of the interaction potential energy surface for the HCNH+–He complex. The aug-cc-pVTZ Gaussian basis, to which is added a set of bond functions placed at mid-distance between HCNH+ center of mass and He atom is used. The HCNH+ bonds length are set to their values at the equilibrium geometry, i.e., r e [HC]=1.0780 Å, r e [CN]=1.1339 Å and r e [NH]=1.0126 Å. The interaction energy presents a global minimum located $266.9~\mathrm{cm^{-1}}$ below the HCNH+–He dissociation limit. Using the interaction potential obtained, we have computed rotational excitation cross sections in the close-coupling approach and downward rate coefficients at low temperature (T≤120 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments.  相似文献   

17.
A high-resolution sunspot umbra spectrum recorded in National Solar Observatory, Kitt Peak in the visible and infrared wave number range 13, 600 – 25, 000cm−1 was taken in the present study for identifying the rotational lines of barium hydride (BaH) molecule. Number of chance coincidences was evaluated for the A 2Π1/2 – X 2Σ ((0,0), (1,1), (2,2), (1,0), (2,1)), A 2Π3/2 – X 2Σ ((0,0), (1,1), (2,2)), B 2Π1/2 – X 2Σ (0,0), B 2Π3/2 – X 2Σ (0,0), C 2Σ – X 2Σ ((1,1), (1,0), (2,2), (2,1), (3,2)) and D 2Σ – X 2Σ ((1,0), (2,0), (3,0), (4,0), (5,0), (8,0), (9,0)) band systems of BaH using line identification procedure. The obtained number of chance of coincidences was compared with I- parameter values. The highly resolved rotational lines were chosen to evaluate equivalent widths using triangle approximation method. The effective rotational temperatures were calculated for the bands (0,0), (1,1), (2,2) and (2,1) of A 2Π1/2 – X 2Σ, (0,0) (1,1) and (2,2) of A 2Π3/2 – X 2Σ, B 2Π1/2 – X 2Σ (0,0) and B 2Π3/2 – X 2Σ (0,0) of BaH molecule. The rotational temperature values calculated for these bands were found to be in the range 1185 – 3514 K. They were also compared with the already reported sunspot temperatures.  相似文献   

18.
Lis  D. C.  Mehringer  D. M.  Benford  D.  Gardner  M.  Phillips  T. G.  Bockelée-Morvan  D.  Biver  N.  Colom  P.  Crovisier  J.  Despois  D.  Rauer  H. 《Earth, Moon, and Planets》1997,78(1-3):13-20
We present millimeter-wave observations of HNCO, HC3N, SO, NH2CHO, H13CN, and H3O+ in comet C/1995 O1 (Hale-Bopp)obtained in February–April, 1997 with the Caltech Submillimeter Observatory (CSO). HNCO, first detected at the CSO in comet C/1996B2 (Hyakutake), is securely confirmed in comet Hale-Bopp via observations of three rotational transitions. The derived abundance with respect to H2O is (4-13) × 10-4. HC3N, SO, and NH2CHO are detected for the first time in a comet. The fractional abundance of HC3N based on observations of three rotational lines is (1.9 ± 0.2) × 10-4. Four transitions of SO are detected and the derived fractional abundance, (2-8) ×10-3, is higher than the upper limits derived from UV observations of previous comets. Observations of NH2CHO imply a fractional abundance of (1-8) × 10-4. H3O is detected for the first time from the ground. The H13CN (3-2)transition is also detected and the derived HCN/H13CN abundance ratio is 90 ± 15, consistent with the terrestrial12C/13C ratio. In addition, a number of other molecular species are detected, including HNC, OCS, HCO+, CO+, and CN(the last two are first detections in a comet at radio wavelengths). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
A study has been made using a variable temperature flowing afterglow Langmuir probe technique (VT-FALP) to determine the equilibrium temperature dependencies of the dissociative electron-ion recombination of the protonated cyanide ions (RCNH+, where R=H, CH3 and C2H5) and their symmetrical proton-bound dimers (RCNH+NCR). The power law temperature dependencies of the recombination coefficients, αe, over the temperature range 180 to 600 K for the protonated ions are αe(T)(cm3 s−1)=3.5±0.5×10−7 (300/T)1.38 for HCNH+, αe(T)=3.4±0.5×10−7 (300/T)1.03 for CH3CNH+, and αe(T)=4.6±0.7×10−7 (300/T)0.81 for CH3CH2CNH+. The equivalent values for the proton-bound dimers are αe(T)(cm3 s−1)=2.4±0.4×10−6(300/T)0.5 for (HCN)2H+ to αe(T)=2.8±0.4×10−6(300/T)0.5 for (CH3CN)2H+, and αe(T)=2.3±0.3×10−6(300/T)0.5 for (CH3CH2CN)2H+. The relevance of these data to molecular synthesis in the interstellar medium and the Titan ionosphere are discussed.  相似文献   

20.
The absolute cross-sections for the excitation of the 989 Å, 1027 Å, 7990 Å, 8446 Å, 1.1287 μm and 1.3164 μm multiplets of atomic oxygen by electron impact dissociation of O2 are reported. The radiative branching ratios for these transitions are calculated from these results and compared with the NBS compilation of Wiese et al. (1966) and the recent theoretical calculations of Pradhan and Saraph (1977). The cascade models of O+ radiative recombination and of electron-impact excitation of the OI(3S) state in the terrestrial airglow are discussed in the light of the laboratory measurements, and the effects of the resonant absorption of components of the λ 989 Å and λ. 1027 Å multiplets by the Birge-Hopfield band system of N2 are investigated. This process is shown to depend sensitively on the N2 vibrational temperature and to cause characteristic changes in the OI e.u.v. emission spectrum in auroras and in the sunlit F-region at high exospheric temperatures. It is also suggested that the λ 1027 Å radiation observed in auroral spectra is actually due to molecular nitrogen band emission that has been enhanced by entrapment effects and not to the excitation of the 2p 3P-3d 3D0 transition of atomic oxygen as believed previously.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号