Air-broadened line widths of methane at atmospheric temperatures

Air-broadened half-widths of lines R(0), R(1) and R(2) in the ν₃-fundamental of ¹²CH₄ have been measured at 200°K, 250°K and 300°K.     

Intensity measurements in the v4-fundamental of methane

The absolute intensities of all the J-multiplets between R(13) at 1375cm^-1 and P(12) at 1225 cm^-1, in the v₄-fundamental of ¹²CH₄, have been measured at 300°K. Our values are consistent with published band-intensity measurements and also with the theoretical line strength tabulation by Fox. Spectral transmittance computation using a Lorentz line shape with a hydrogen-broadened half-width of 0.075 cm^-1 atm^-1 at 300°K for all the lines in the band is in excellent agreement with our experimental data measured with a spectral resolution of 0.2 cm^-1. Our best estimate for the absolute intensity of the band is 145±8 cm^-2 atm^-1 at STP.     

Measurement of intensities of multiplets in the 2ν3-band of methane at low temperatures

The integrated intensities of the multiplets P(1)–P(10), R(0)–R(9), and of the Q-branch in the 2ν₃-band of ¹²CH₄ have been measured at 102°K, 152°K, 202°K, 251°K, and 300°K. Comparison of our data with theoretical line strengths confirms, at all of the temperatures mentioned, the intensity anomalies observed by Margolis⁽⁵⁾ for lines in this band. The integrated intensity of the 2ν₃-band is found to be S_v = (1·76±-0·04)(300/T (°K)) cm^?2 atm^?1.     

Resonant widths, line intensities and lineshapes for MQDT models with two or more open channels

Approximate analytical formulae describing the energy variation of line intensities, autoionization widths and lineshape asymmetries, are derived for a Phase-Shifted Multichannel Quantum Defect Theory model composed of two closed interacting channels coupled to two effective continua. This is accomplished by putting the two compatibility equation solutions, for the common phase shifts of the two open channels, in such a form so the resonant behavior is attributed to one of them, the other accounting for an energy dependent background. Then, the well-known procedures for the simpler case where only one continuum is considered are applied, using only the resonant solution. The method is quite general and applicable to any MQDT model with two or more open channels. The resulting analytical formulae are tested on experimental spectra of Sr, Ba and Cu and it is shown that they are valid as long as: i) The resonances are non-overlapping, ii) The direct closed channel coupling is much stronger than the indirect one through the continua and (when excitation matrix elements are involved) iii) The open channels excitation strength is smaller or at least comparable to the closed channels one. Received: 26 May 1998 / Accepted: 1st July 1998     

Measurement of line intensities of linear molecules under low resolution

By using the relation k_v?S_J/δ_J applicable at sufficiently high pressures, at which the rotational fine structure in a band is smeared out completely, line intensities S_J may be determined from measured spectral absorption coefficients and known local line spacings δ_J. First, the validity of the approximation is ascertained by comparing the spectral absorption coefficient data of Penner and Weber and of Varanasi and Penner for the fundamental bands of CO and NO, respectively, with S_J/δ_J derived from the high resolution measurements of Benedict et al. (for CO) and of Abels and Shaw (for NO). Line intensity data obtained using this method are in good agreement with the high-resolution measurements of Toth (grating spectroscopy) for some unblended lines in the 00°0?02°1 band of N₂O and of Lacome et al. (laser- spectroscopy) for lines in the 10°0?00°1 band of N₂O.     

Measurement of line widths of CO of planetary interest at low temperatures

Self-broadened, air-broadened and CO₂-broadened half-widths of lines R(0) through R(0) in the CO fundamental have been measured at 100°K (self-broadening only), 200°K, 250°K and 300°K using the Ladenburg-Reiche curve-of-growth. The relation $\text{γ}{}^{\mathrm{°}}{}_{\mathrm{m}}\text{(T)}\text{γ}{}^{\mathrm{°}}{}_{\mathrm{m}}\text{(300°K)}\text{=(}\text{300}\text{T}\text{)}{}^{0.75}$, which we found previously for the nitrogen-broadened half-widths of R(0), R(8) and R(16), is shown to be valid for all of the line widths measured in the present study.     

Regularities and similarities in plasma broadened spectral line widths (Stark widths)

Regularities and similarities in plasma broadened line widths have been studied by a comprehensive analysis of existing experimental data. Regularities are expected on the basis of general atomic structure considerations, and should be evident for spectral series, for corresponding transitions in homologous atoms and in isoelectronic sequences. Furthermore, similarities of line widths are expected for multiplets, supermultiplets and, to a lesser degree, for transition arrays. A comprehensive examination of literature data has been undertaken, which shows generally a close adherence of the measured data to the expected regularities. A few notable exceptions are also given.     

Spectral line intensities of Yb3+ ion in LiNbO3 crystals

Optical spectra of absorption and luminescence of LiNbO₃:Yb³⁺ crystals are investigated experimentally and theoretically. Within the framework of the point charge approximation of crystal field, the Stark problem is solved: crystal field parameters and wave functions of Stark states are determined. Line strengths due to indirect electric-dipole and magnetic-dipole inter-Stark transitions are calculated and values of the Judd-Ofelt parameters are determined. Values of the branching ratios of luminescence. Einstein coefficients and, lifetime of the excited sublevel are calculated. A satisfactory agreement of calculated results with experimental data is obtained.     

Precision measurements of x-ray energies,natural widths and intensities in the actinide region

A Dumond-type curved crystal spectrometer has been used to measureK x-ray energies, natural widths and relative intensities for the eleven actinides from₈₈Ra to₉₈Cf. The results are compared to the most recent theoretical predictions.     

Pressure broadened line widths of BrCN in the microwave region

The line widths of cyanogen bromide (BrCN) have been measured at room temperature (305 K) by using a double modulation microwave spectrograph. The self-broadening of two quadrupole hyperfine lines of the transition J = 3 → 4 has been measured. The foreign gas broadening by OCS, CO₂, N₂, CH₃CN, CH₃I, HCHO and CH₃CHO molecules has been measured only for the intense line at 32·957 GHz. These measured line widths have been compared with the calculated line widths using Anderson [6] as well as Murphy and Boggs [8] theories of pressure broadening.     

对称陀螺分子NH3的高温谱线强度研究

在直接计算分子配分函数的基础上,将无转动跃迁偶极矩平方近似为一常数,计算了对称陀螺分子NH3,0300a-0000 s跃迁在高温下的线强度.在296 K,计算的分子总配分函数与HITRAN数据库的结果符合很好,只有O.19%的百分误差.计算的跃迁线强度在2000 K和3000 K的高温与HITRAN数据库的结果也符合相当好,最大百分误差分别为-0.65%和-1.77%.这就表明分子配分函数和线强度的高温计算是可靠的.在此基础上,计算被扩展到更高温度,报道了对称陀螺分子NH30300 a-0000 s跃迁在极端高温4000和5000 K的模拟光谱.计算结果对大气分子高温光谱的实验测量和理论研究均有一定的参考价值.     

Effect of hydrogen bonding on the Rayleigh and Raman line widths

A study was made of the broadening of the Rayleigh-scattering line of nitromethane solutions in chloroform, benzene, acetone, and CCl₄. The scattering line contracts in the chloroform solutions but is unaffected in the other solutions. The results are attributed to a decrease in the ability of the molecules to rotate as a result of the formation of nitromethane-chloroform associations; A pronounced contraction of the 1591 cm^–1 line is observed in the Raman spectra of the chloroform solution. The other lines studied displayed no appreciable contraction in the transition from the pure liquid to the solutions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 7–11, November, 1970.     

Third-order theory of the line intensities in the allowed and forbidden vibrational-rotational bands of C3v molecules

A third-order theory of the intensities of the allowed and “forbidden” (perturbation-allowed) transitions to the fundamental vibrational levels of C_3v semirigid molecules has been worked out by using the method of contact transformations applied to the electric dipole moment operator. Explicit expressions have been obtained for the linestrengths of the allowed (Δk = 0, ±1) as well as forbidden (Δk = ±2, ±3, ±4) transitions from the ground vibronic state to the fundamental vibrational levels of C_3v molecules. The treatment takes into account all the important Coriolis and anharmonic interactions in a C_3v molecule, including the effect of the “2, 2” and “2, −1” l-type interactions and the Δk = ±3 interactions on the intensities of the allowed and forbidden vibrational-rotational transitions. The expressions for the linestrengths of the allowed and forbidden transitions are given here in a form suitable to fit the experimental data on the intensities in the vibrational-rotational spectra of C_3v molecules.     

The temperature dependence of the Rayleigh line wing and depolarized combinational scattering line widths in critical mixtures

It has been experimentally found that at approaching the critical temperature of the exfoliating mixture carbon-disulfide-ethanol the widths of the Rayleigh line wing and the depolarized combinational scattering line drastically decrease. The same phenomenon was observed for 3 nitrobenzene combinational line scattering in a nitrobenzene—n-hexane mixture.     

On the variation of spectral line widths within stark-broadened multiplets

The Stark broadening of isolated ion lines is considered in the electron impact approximation. It is shown by an elementary formulation of the theory that, under certain plasma conditions, situations may arise in complex atoms where a relatively small number of collision-induced transitions predominate in the broadening, and consequently where appreciable variations of spectral line width are obtained within multiplets. Such lines are then particularly suitable for application of the Stark-broadening mechanism as a means of studying atomic structure and collision physics.     

Measurements of line intensities in the two-micron band of ammonia

Intensities of about four hundred lines of ammonia in the 2μ region have been measured using Doppler-broadened lines. Comparison with rigid-rotor calculations gives fair agreement between theory and experiment. The total integrated intensity of the ν₃ + ν₄ (perpendicular) band has been estimated to be 17.19 cm^-2 atm^-1 at 296 K.     

Effect of collision-induced phase-shifts on the line widths and line shifts of CO2-Ar system

The theoretical calculation of line widths and line shifts for CO₂-Ar system is computed by the Mehrotra-Boggs theory. It is shown for this system that the phase shift effect is very important at large values of |m| wherem is the value of rotational quantum numberJ in the lower vibrational state. It is also pointed out that the Salesky-Korff theory is the same as the Mehrotra-Boggs theory.     

Evidence of anomalous multiplet line shapes in optically thick,laser-produced plasmas

We report observations of anomalous line shapes for the transitions 2p?3d (²P?²D) emitted by the Li-like ions N(V), O(VI), F(VII) in laser-produced plasmas. These transitions are normally doublets but show completely different characteristics (e.g., triplet structures or invension of two-component intensity ratios) in the plasmas. The observed line profiles are accounted for in terms of opacity and Doppler effect produced by plasma expansion. This interpretation is independent of the particular transition involved, i.e., multiplet structures can generate more complicated features with various unexpected new components, anomalous intensity ratios, etc.