Sodium resonances in fluorescence from wide-range laser scan in H2-O2-Ar flame

Several resonances and underlying continua were observed in the excitation profiles of sodium atoms in an H₂-O₂-Ar flame, irradiated by the focused beam of a tunable, pulsed dye layer. These profiles are obtained by tuning the laser through the spectral range of Rhodamine 6G and detecting the ensuing fluorescence signals from the 3D-3P and 4D-3P transitions. We observed resonances corresponding to the 3S_{$\text{1}\text{2}$}-3P_{$\text{1}\text{2}$}, 3S_{$\text{1}\text{2}$}-3P_{$\text{3}\text{2}$}, 3P_{$\text{1}\text{2}$}-5S_{$\text{1}\text{2}$}, 3P_{$\text{3}\text{2}$}-5S_{$\text{1}\text{2}$} one-photon transitions and resonances corresponding to the 3S_{$\text{1}\text{2}$}-5S_{$\text{1}\text{2}$}, 3S_{$\text{1}\text{2}$}-4D_{$\text{3}\text{2}$}, _{$\text{5}\text{2}$} two-photon transitions. The observed resonances result from different sequences of radiative and collisional excitation. The presence of the continua is explained by consecutive absorption of laser photons in the collisionally broadened wings of absorption lines. The spatial inhomogeneity of the laser beam and hence of the saturation causes submerging of some resonances into continua.     

Ignition by moving hot spheres in H2-O2-N2 environments

A combined experimental and numerical study was carried out to investigate thermal ignition by millimeter size ($d=6$ mm) moving hot spheres in H₂-O₂-N₂ environments over a range of equivalence ratios. The mixtures investigated were diluted with N₂ to keep their laminar flame speed constant and comparable to the sphere fall velocity (2.4 m/s) at time of contact with the reactive mixture. The ignition thresholds (and confidence intervals) were found by applying a logistic regression to the data and were observed to increase from lean ($\Phi =0.39$; T_sphere = 963 K) to rich ($\Phi =1.35$; T_sphere = 1007 K) conditions. Experimental temperature fields of the gas surrounding the hot sphere during an ignition event were, for the first time, extracted using interferometry and compared against simulated fields. Numerical predictions of the ignition thresholds were within 2% of the experimental values and captured the experimentally observed increasing trend between lean and rich conditions. The effect of stoichiometry and dilution on the observed variation in ignition threshold was explained using 0-D constant pressure delay time computations.     

A precise study of the rotational spectrum of formaldehyde H2CO, H2CO, H2CO, H2CO

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

Full-size image

     

The OH collision broadening parameter in the 2900°K H2-NO flame

The collision broadening parameter of the Q₁6 line in the OH (0, 0) A → X u.v. transition has been determined by the curve of growth method in atmospheric pressure nitric oxide-hydrogen flames, in the temperature range 2800–2900°K. An average value of 0.05 was found for this parameter for five flames varying in feed composition between 40 and 65% NO. The exact flame gas compositions and temperatures for which these determinations were made are given in the paper. The data obtained are in agreement with those obtained by Carrington² for atmospheric hydrogen-oxygen flames at 2600°K.     

Collisional redistribution of radiatively-excited levels of Tl and Ga atoms in an O2-acetylene-Ar flame

Several useful expressions for the population ratios of collisionally excited levels have been derived and different transitions of Tl and Ga atoms, seeded in a premixed atmospheric flame, have been excited in order to verify that the levels higher than the laser-excited level are populated approximately according to a Boltzmann equilibrium. This result confirms the possibility of using thermally assisted flourescence lines to measure local temperatures in flames. The Einstein spontaneous emission probability for the transition 6S_1/2→4P_3/2 at 2719.65Å of Ga has also been calculated (A_2719.65=0.41×10⁸s^-1) to fit the experimental point.     

Direct measurements of lifetimes of excited levels in H2O+

Lifetimes of ten different bands belonging to the recently discovered ²A₁-²B₁ system in H₂O⁺ have been directly measured using the high frequency deflection technique. The measured lifetimes are all consistent with a value around 800 ns.     

The Rotational Spectra of H2CCSi and H2C4Si

The microwave rotational spectra of two singlet chains H₂CCSi and H₂C₄Si, have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. Following detection of the singly substituted rare isotopic species and D₂CCSi, an experimental structure (r₀) has been determined to high accuracy for H₂CCSi by isotopic substitution. In addition, the rotational transitions of the ²⁹Si and the two ¹³C isotopic species of H₂CCSi exhibit nuclear spin-rotation hyperfine structure. The component of the spin-rotation tensor along the a-inertial axis is abnormally large for each of these isotopic species, especially for that with ²⁹Si, where the magnitude of C_aa is in excess of 700 kHz.     

He—H2碰撞过程中的H2分子的振动激发

用半径典模型描述原子A与双原子分子B－C的共线碰撞,分子B－C的振动激发,近似用线性外场中的变频振子描述,应用不变量方法求出He和H2碰撞过程中H2分子从基态到所有振动激发态的跃迁几率。     

Spectroscopically determined potential energy surfaces of the H2O, H2O, and H2O isotopologues of water

Adiabatic potential energy surfaces (PESs) for three major isotopologues of water, H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O, are constructed by fitting to observed vibration-rotation energy levels of the system using the nuclear motion program DVR3D employing an exact kinetic energy operator. Extensive tests show that the mass-dependent ab initio surfaces due to Polyansky et al. [O.L. Polyansky, A.G. Császár, S.V. Shirin, N.F. Zobov, P. Barletta, J. Tennyson, D.W. Schwenke, P.J. Knowles, Science 299 (2003) 539-542.] provide an excellent starting point for the fits. The refinements are performed using a mass-independent morphing function, which smoothly distorts the original adiabatic ab initio PESs. The best overall fit is based on 1788 experimental energy levels with the rotational quantum number J = 0, 2, and 5. It reproduces these levels with a standard deviation of 0.079 cm⁻¹ and gives, when explicit allowance is made for nonadiabatic rotational effects, excellent predictions for levels up to J = 40. Theoretical linelists for all three isotopologues of water involved in the PES construction were calculated up to 26 000 cm⁻¹ with energy levels up to J = 10. These linelists should make an excellent starting point for spectroscopic modelling and analysis.     

Second-order conditional moment closure modeling of a turbulent CH4/H2/N2 jet diffusion flame

The second-order CMC model for a detailed chemical mechanism is used to model a turbulent CH₄/H₂/N₂ jet diffusion flame. Second-order corrections are made to the three rate limiting steps of methane–air combustion, while first-order closure is employed for all the other steps. Elementary reaction steps have a wide range of timescales with only a few of them slow enough to interact with turbulent mixing. Those steps with relatively large timescales require higher-order correction to represent the effect of fluctuating scalar dissipation rates. Results show improved prediction of conditional mean temperature and mass fractions of OH and NO. Major species are not much influenced by second-order corrections except near the nozzle exit. A parametric study is performed to evaluate the effects of the variance parameter in log-normal scalar dissipation PDF and the constants for the dissipation term in conditional variance and covariance equations.     

Collisional broadening and shifting of the 211-202 transition of H2O, H2O, H2O by atmosphere gases

Broadening and shifting of the 2₁₁-2₀₂ transition of H₂¹⁶O, H₂¹⁷O, H₂¹⁸O by pressure of water, nitrogen and oxygen were precisely measured at room temperature using spectrometer with radio-acoustic detection of absorption. Shift parameters for all studied lines as well as broadening parameters of H₂¹⁷O, H₂¹⁸O lines were measured for the first time. Comparison of obtained results with previously known experimental and theoretical data is presented.     

Analysis of ν2 of H233S and H234S

We have extended our analysis of the (010) vibrational state of H₂S, this time using Watson's A-reduced Hamiltonian (through P⁸ terms) in the I′ rotational representation. We have determined separate sets of (010) upper state constants for each isotopomer (H₂³²S, H₂³³S, and H₂³⁴S) by fitting the ν₂ spectral lines, keeping the ground state constants fixed to the values determined by Flaud, Camy-Peyret, and Johns. Determinable coefficients for H₂³²S and a slightly revised set of ν₂ line assignments for H₂³³S and H₂³⁴S are also reported.     

A precise study of the rotational spectrum of formaldehyde H212C16O,H213C16O,H212C18O,H213C18O

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

     

14.

Centrifugal distortion analysis of pure rotational spectra of H₂¹⁶O,H₂¹⁷O,and H₂¹⁸O     

E. Kyrö 《Journal of Molecular Spectroscopy》1981,88(1):167-174

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

15.

RHEED and Auger study of the MoO₃(010) surface interaction with H₂S/H₂ mixture and pure H₂S     

A. Steinbrunn  C. Lattaud 《Surface science》1985,155(1):279-295

Pure single crystals of MoO₃ were carefully grown by physical vapor transport. The initial stages of the interaction of H₂S with a MoO₃ (010) surface were studied by RHEED and AES at low pressure p <133 Pa and at T < 700 K. Three main stages were found: (a) The formation of either a completely disordered sulphur adiayer (with pure H₂S) or a superstructure MoO₃(010)-[2 × 1]S (with H₂S/H₂). (b) A reduction of MoO₃ producing oriented three-dimensional MoO₂ islands, (c) An epitaxial overgrowth of MoS₂ from the MoO₂ three-dimensional crystallites.     

16.

Redistribution of deuterium atoms in HfV2Dx compounds     

I. G. Ratishvili  N. Z. Namoradze 《Physics of the Solid State》2001,43(2):199-206

A solution of hydrogen in the AB₂ intermetallic compound with a C-15 structure is considered. The ordering of hydrogen atoms is investigated, which consists in forming their unequal distribution among the sub-lattices of the A₂B₂ interstices. It is demonstrated on the basis of qualitative analysis and numerical calculations that, in HfV₂D_x compounds, the evolution of the redistribution of the interstitial atoms and their low-temperature order can be different depending on the hydrogen content in the solution and the energy parameter of the system p≡V ₂/V ₁.     

17.

Penning ionization electron spectroscopy of H₂O,D₂O,H₂S and SO₂     

V. Čermák  Andrew J. Yencha 《Journal of Electron Spectroscopy and Related Phenomena》1977,11(1):67-73

Electron energy peak shifts and peak shapes were determined in the ionization of H₂O, D₂O, H₂S and SO₂ by Ne(³P₂) and He(2¹S, 2³S) metastable atoms. The shifts are large, especially in ionization of H₂O and D₂O into the ionic ground state and are probably mostly due to chemical interaction during the collision.In a previous paper the electron energy distribution curves for ionization of CO, HCl, HBr, N₂O, NO₂, CO₂, COS and CS₂ by helium, neon and argon metastables and the characteristics of this ionization were described¹. In this paper the series of triatomic molecules was extended to the molecules H₂O, D₂O, H₂S and SO₂. Because all these molecules have considerable dipole moments it could be expected that the peak shifts might be enhanced as compared with other triatomic molecules.     

18.

Velocity dependence of the chemi-ionization of H₂O and D₂O on impact of 2¹S and 2³S helium atoms     

W. Allison  E.E. Muschlitz 《Journal of Electron Spectroscopy and Related Phenomena》1981,23(3):339-346

The velocity dependence for the ionization of H₂O and D₂O to form H₂O⁺ and D₂O⁺ in collisions with both 2³S and 2¹S metastable helium atoms has been measured in a crossed molecular beam apparatus using a mechanical velocity-selector on the metastable beam. The cross-sections are found to be proportional to the —n power of the relative collision energy, with n ? 0.4 for both metastable atoms in both gases. The branching ratios H₂O⁺/OH⁺ and D₂O⁺/OD⁺ were both found to be 4.3 for both metastable helium atoms, and to be independent of the relative collision energy.     

19.

Carbon-13 Isotopic Species of H₂C₃, H₂C₄, and H₂C₅: High-Resolution Rotational Spectra     

M.C. McCarthyP. Thaddeus 《Journal of Molecular Spectroscopy》2002,211(2):235-240

The microwave rotational spectra of the carbon-13 isotopic species of H₂C₃, H₂C₄, and H₂C₅ have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. At high resolution all of the rotational lines exhibit hyperfine structure produced by the magnetic interaction between the nuclear spin of ¹³C and the overall rotation of the molecule. The component of the nuclear spin-rotation tensor along the a-inertial axis is large for most isotopic species, especially at the carbene carbon; at this position C_aa is two to three times larger than at other substituted positions along the chain. In contrast to both H₂C₃ and H₂C₃, in H₂C₄C_aa exhibits a pronounced alternation along the carbon chain backbone. Following detection of the five carbon-13 isotopic species and D₂C₅, an experimental structure (r₀) has been determined to high accuracy for H₂C₅.     

20.

Si在水汽中氧化传质机制的H₂¹⁸O/H₂¹⁶O同位素示踪研究          下载免费PDF全文

龚佳  蒋益明  钟澄  邓博  刘平  李劲 《物理学报》2009,58(2):1305-1309

采用同位素H₂¹⁶O/H₂¹⁸O接续氧化同位素示踪方法,研究了单晶硅在1100 ℃水汽中氧化的微观传质机制.在H₂¹⁶O,H₂¹⁸O分别氧化和H₂¹⁶O/H₂¹⁸O接续氧化处理后,研究氧化产物形态和结构.并用二次离子质谱仪(SIMS)研究了同位素 关键词： 同位素示踪 2¹⁸O')" href="#">H₂¹⁸O 替位扩散 硅     

	H212C16O	H213C16O	H212C18O	H213C18O
A/MHz	281 970.572 (24)	281 993.258(135)	281 961.94 (39)	281 985.00 (93)
B/MHz	38 836.0456(13)	37 811.0887(25)	36 904.1693(66)	35 859.256(10)
C/MHz	34 002.2034(12)	33 213.9790(25)	32 511.5311(63)	31 697.868(10)

Centrifugal distortion analysis of pure rotational spectra of H216O,H217O,and H218O

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

RHEED and Auger study of the MoO3(010) surface interaction with H2S/H2 mixture and pure H2S

Pure single crystals of MoO₃ were carefully grown by physical vapor transport. The initial stages of the interaction of H₂S with a MoO₃ (010) surface were studied by RHEED and AES at low pressure p <133 Pa and at T < 700 K. Three main stages were found: (a) The formation of either a completely disordered sulphur adiayer (with pure H₂S) or a superstructure MoO₃(010)-[2 × 1]S (with H₂S/H₂). (b) A reduction of MoO₃ producing oriented three-dimensional MoO₂ islands, (c) An epitaxial overgrowth of MoS₂ from the MoO₂ three-dimensional crystallites.     

Redistribution of deuterium atoms in HfV2Dx compounds

A solution of hydrogen in the AB₂ intermetallic compound with a C-15 structure is considered. The ordering of hydrogen atoms is investigated, which consists in forming their unequal distribution among the sub-lattices of the A₂B₂ interstices. It is demonstrated on the basis of qualitative analysis and numerical calculations that, in HfV₂D_x compounds, the evolution of the redistribution of the interstitial atoms and their low-temperature order can be different depending on the hydrogen content in the solution and the energy parameter of the system p≡V ₂/V ₁.     

Penning ionization electron spectroscopy of H2O,D2O,H2S and SO2

Electron energy peak shifts and peak shapes were determined in the ionization of H₂O, D₂O, H₂S and SO₂ by Ne(³P₂) and He(2¹S, 2³S) metastable atoms. The shifts are large, especially in ionization of H₂O and D₂O into the ionic ground state and are probably mostly due to chemical interaction during the collision.In a previous paper the electron energy distribution curves for ionization of CO, HCl, HBr, N₂O, NO₂, CO₂, COS and CS₂ by helium, neon and argon metastables and the characteristics of this ionization were described¹. In this paper the series of triatomic molecules was extended to the molecules H₂O, D₂O, H₂S and SO₂. Because all these molecules have considerable dipole moments it could be expected that the peak shifts might be enhanced as compared with other triatomic molecules.     

Velocity dependence of the chemi-ionization of H2O and D2O on impact of 21S and 23S helium atoms

The velocity dependence for the ionization of H₂O and D₂O to form H₂O⁺ and D₂O⁺ in collisions with both 2³S and 2¹S metastable helium atoms has been measured in a crossed molecular beam apparatus using a mechanical velocity-selector on the metastable beam. The cross-sections are found to be proportional to the —n power of the relative collision energy, with n ? 0.4 for both metastable atoms in both gases. The branching ratios H₂O⁺/OH⁺ and D₂O⁺/OD⁺ were both found to be 4.3 for both metastable helium atoms, and to be independent of the relative collision energy.     

Carbon-13 Isotopic Species of H2C3, H2C4, and H2C5: High-Resolution Rotational Spectra

The microwave rotational spectra of the carbon-13 isotopic species of H₂C₃, H₂C₄, and H₂C₅ have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. At high resolution all of the rotational lines exhibit hyperfine structure produced by the magnetic interaction between the nuclear spin of ¹³C and the overall rotation of the molecule. The component of the nuclear spin-rotation tensor along the a-inertial axis is large for most isotopic species, especially at the carbene carbon; at this position C_aa is two to three times larger than at other substituted positions along the chain. In contrast to both H₂C₃ and H₂C₃, in H₂C₄C_aa exhibits a pronounced alternation along the carbon chain backbone. Following detection of the five carbon-13 isotopic species and D₂C₅, an experimental structure (r₀) has been determined to high accuracy for H₂C₅.     

Si在水汽中氧化传质机制的H218O/H216O同位素示踪研究

采用同位素H₂¹⁶O/H₂¹⁸O接续氧化同位素示踪方法,研究了单晶硅在1100 ℃水汽中氧化的微观传质机制.在H₂¹⁶O,H₂¹⁸O分别氧化和H₂¹⁶O/H₂¹⁸O接续氧化处理后,研究氧化产物形态和结构.并用二次离子质谱仪(SIMS)研究了同位素 关键词： 同位素示踪 2¹⁸O')" href="#">H₂¹⁸O 替位扩散 硅