Shift Of Emission Lines Research Articles

SCF Xα SW calculations of chemical shifts of X-ray and electron emission lines and relaxation properties of SiX 4 molecules

SCF Xα SW calculations of the 1s and 2p binding energies, KLL Auger energies and Kα transition energies for the molecules SiH 4, SiCl 4 and SiF 4 and the corresponding atomic Xα calculations for charged free silicon ions have been carried out. The results provide information about relaxation properties and anomalous chemical Kα shifts in hydrides.

Broadening and shift of emission lines during nonlinear transfer in a turbulent plasma

Broadening and shift of emission lines during nonlinear transfer in a turbulent plasma

A comparison of self broadening and shift of helium, neon and argon emission lines

Self broadening (van der Waals and resonance) and shift of Ne emission lines and van der Waals broadening and shift of He emission lines have been measured using a high pressure (0.5–3.0 atom), low current discharge. These results are compared with previous measurements in Ar and He to obtain a complete comparison of self broadening and shift of He, Ne and Ar emission lines. Oscillator strengths for the resonance transitions are obtained from the resonance broadening coefficients. The trend of the van der Waals broadening coefficients for the three noble gases is correctly predicted by a theory due to HINDMARSH et al. (4) in which a Lennard-Jones potential is used in the impact theory formalism. The measured line shifts cannot be accounted for by this theory and reflect the need for more accurate quantum mechanical calculations.

A comparison of foreign gas broadening and shift of neon and argon emission lines

Foreign gas broadening and shift coefficients for Ne and Ar emission lines produced in a high pressure (0·5-2·0 atm) He discharge have been measured. The shift coefficients vary significantly for different transitions. This variation results from the differing excited state potentials for the He-Ne ∗ and He-Ar ∗ collision pairs, which must be included in any reasonable quantum-mechanical calculation of line shifts. Even the small differences in broadening coefficients demonstrate the inadequacy of calculation of broadening from equations based on the Lindholm (1)-Foley (2) theory of collision broadening.

Optical Absorption of Molecules in Liquid Solutions in an Applied External Electric Field (Electrochromism)

AbstractA sufficiently strong applied electric field causes a shift and splitting of absorption and emission lines in atomic spectroscopy well known as Stark effect. With molecules usually only a field dependent change of the absorption and emission coefficient can be observed, a phenomenon called electrochromism. The various reasons which contribute to electrochromism are treated in this paper. Emphasized are the effects of the solvent molecules on the effective electric field causing additional contributions to electrochromism in solutions or other dense media compared to electrochromism in a gaseous phase.

High resolution emission spectra of laser-excited molecular iodine as the excitation frequency is tuned through and away from resonance

We have studied the Δ J = 2 rotationally shifted emission lines in the region of the strong absorption of molecular iodine which occurs within the 5145 Å argon ion laser line. We used an etalon tuned, single frequency argon ion laser with a linewidth of 20 MHz to excite the iodine emission and recorded the spectra of the rotational lines with Fabry-Perot spectrometers having resolutions up to 70 MHz (0.0023 cm -1). To overcome Doppler linewidth limitations we took spectra of the emission at small angles to the exciting beam and found the lines to have widths less than our instrumental resolution and frequencies which accurately tuned with the incident laser frequency. We recorded the emission lines for laser frequencies in the absorption line center and out into the absorption wing. Our spectra show that the intensity of the emission lines follows the absorption line profile while the frequency of the emission lines is determined by the laser frequency; the intensity is maximum at the absorption line center, falling by 10 4 as the laser frequency is moved off the line center, while the line position maintains a constant frequency shift from the laser frequency.

Pressure broadening and shift of argon emission lines

Resonance and van der Waals broadening coefficients, as well as width to shift ratios, have been obtained by scanning argon emission lines produced in a high-pressure (∼ 1 atm) glow discharge at a temperature of 1130°K. The resonance broadening coefficients yield absolute oscillator strengths of 0·283 ± 0·024 and 0·076 ± 0·008 for the two resonance lines at 1048 Å and 1067 Å. These oscillator strengths are in good agreement with previous measurements. The importance of higher-order terms in the van der Waals potential expansion is demonstrated by the measured coefficients.

A new method for measuring the chemical shifts of X-ray emission lines and its application in electron microprobe analysis

A new formula for calculating the chemical shift of X-ray lines is theoretically derived. A test of the method is given as well as its application in electron microprobe analysis for the purpose of obtaining some crystal-chemical characteristics of solids.

The charge distribution in chromium(III) and iron(III) hexafluoride

Semi-empirical molecular orbital calculations were performed for CrF 3− 6 and FeF 3− 6. The method of calculation is derived from the HF SCF equations using approximations appropriate to the highly ionic transition metal halides. The results of these calculations are shown to be in better agreement than previous semis-empirical calculations with X-ray emission line shifts and atom charges and populations estimated from these shifts.

Determination of Effective Atomic Charges from the Chemical Shifts of X-Ray Emission Lines

The x-ray line shifts obtainable as differences of level shifts from various quantum mechanical calculations using the free-ion model provided values which were in good agreement with each other at least for the Kα shifts. This justifies the determination of effective atomic charges from experimental x-ray line shifts. The formation of inner holes can be taken into account by using the values of Z + 1 for the charge determination of compounds of the element Z. With the 3d elements the Kβ shift must be considered besides the Kα one due to the opposite effects of missing 3d and 4s electrons. The charges determined for the first time only x-ray spectroscopically—generally between 0.8 and 1.5—as well as the 3d and 4s orbital populations change in the same manner as the values obtained from MO calculations. In contrast to the situation with the main group elements where the effective charge increases with increasing formal charge, the former decreases for formal charges above 2 with the 3d elements.

Fizeau interferometer profiles at finite acceptance angles

Instrument profiles of the wedge or Fizeau interferometer are determined under practical conditions. The appearance of subsidiary maxima on the high order side of the central maxima is confirmed, and the behaviour of these is noted as the solid angle of acceptance is varied. From these calculations it is inferred that the acceptable range of use of the instrument could be much wider than was previously believed and that the instrument can be of considerable use in measuring small shifts in spectral emission lines.

The shift of the emission lines of Cr and Ni produced by argon and helium

The shifts of all strong emission lines of neutral Cr and Ni in the wavelenght ranges of 3014–5328 Å, and 3050–3619 Å, respectively, with argon and of 3017–4651 Å and 3369–3619 Å, respectively, with helium have been measured. The temperatures and the relative densities (r.d.) of the gases at which observations were made are, respectively, 3230°K and 28–104 for Ar and 3600°K and 60–108 for He. The shift vs. r.d. relationship for 14 CrI lines and 11 NiI lines with argon, and 12 Cr lines and a single Ni line with helium, are tabulated. Some lines show a linear dependence of shift on r.d. and some behave linearly for low r.d. but quadratically for higher r.d. The general statements about the behavior of the relative shifts of spectral levels with respect to L and S values are the same as those for the FeI lines. The normal fine-structure levels (many multiplets of CrI) behave in their relative shifts oppositely to those of inverted levels (FeI), although the behavior depends on the more detailed structure of the levels.

The shift of iron emission lines produced by argon and helium

The shifts of all the strong emission lines of the neutral iron atom in hot compressed argon and helium (produced by a ballistic compressor) were measured in the region 2497–5900 Å. Curves showing the shift vs. relative density (r.d.) are presented for 68 of these lines with argom and 14 with helium, over a range of r.d. from 28 to 104 at 3230°K for argon and from 36 to 108 at 3600°K for helium. For argon, the relative displacements of various spectral terms of FeI with different J, L, S or electron configurations are discussed. A decrease in red shift was observed at higher temperatures.

Luminescence Spectra of Sm3+ in BaTiO3 Host Lattice

Luminescence spectra of Sm 3+ at a Ti 4+ site in BaTiO 3 host lattice were investigated in a wide range of temperatures including those above the Curie point. Any shifts of emission lines were not observed between -196°C and 145°C. The ferro-to-paraelectric transition is considered not to influence the strength of the electrostatic field surrounding Sm 3+ so much as to induce a detectable shift of the 4 f electron levels. Some singlet lines were found to split into doublets associated with the transitions of the crystal structure from the cubic to tetragonal and also from the rhombohedral to orthorhombic phase. These facts are accounted for by considering the change of the site symmetry around Sm 3+ .

Interpretation of Measurements on Emission Edges in Be Spectra.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interpretation of Measurements on Emission Edges in Be Spectra. McLaughlin, Dean B. Abstract Students of Be spectra differ in their views regarding the apparent shifts of emission lines and their central absorptions (NiicLaughlin, Astrophys. 1. 134,1015, 1961; Under- hill, ibid., p. 1017). In an attempt to resolve this question. the Hp structure was measured on microphotometer tracings of 30 spectrograms of p' Monocerotis, covering the full range of V/R variation. These measures were compared with micrometer settings made directly on the spectrograms. General conclusions are as follows: (1) The position measured as the edge of a strong emission component on the spectrogram is identified as the steepest gradient of density as recorded on the tracing. (2) The measured edge of a weak emission component with uniform gentle gradient is near the halfintensity point of the profile. (3) Assuming that the position of the absorption, as measured on the spectrogram, has been correctly identified on the tracing, the velocities of the en~ssion lines have been obtained. The results confirm the conclusion stated by Merrill (Astrophys. 1. 116,501, 1952): `The emission as a whole shifts in the same direction as the core, but by a smaller amount." Specifically, in p' Monocerotis, the amplitude of emission velocity is between 60 and 70% of that of the absorption velocity. Result (3) disagrees quantitatively with the conelusion drawn from micrometer measures alone. The explanatioi~ probably lies in the manner of measuring weak components (2). When an emission is weak, its edge is measured farther out in the fading wing, which tends to increase the apparent amplitude of emission velocity to approximate equality with that of the central absorption. Publication: The Astronomical Journal Pub Date: March 1962 DOI: 10.1086/108822 Bibcode: 1962AJ.....67Q.277M full text sources ADS |

Attempted Interpretations of V/R Variation in Be Spectra.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Attempted Interpretations of V/R Variation in Be Spectra. McLaughlin, Dean B. Abstract pulsating model for V/R variation (McLaughlin, 1931, Publ. Am. Astron. Soc. 7, 31; 1933, Proc. Natl. Acad. Sci. 19, 44) does not account satisfactorily for some details of the observations. In particular, it fails to yield the large shifts of emission lines in the same direction as the central absorption. Where the absorption varies in strength (as in ~ Mon A) it is weakest at the phase predicted for maximum strength by the rotating-pulsating model. The very large motions implied for cycles of over 1000 days are difficult to admit. Attempts were made to account for the variations by means of a rotating atmosphere subject to intermittent expansion that is alternately accelerated and retarded. Qualitative agreement is obtained only with artificial assumptions that do not appear physically justifiable. Again the shifts of emission lines are not satisfactorily represented. All the observed phenomena do appear explicable by rotation of the line of apsides of elliptical rings of gas, as originally suggested by Struve (1931, A strophys. J. 73' 94). Periastron at the receding node gives maximum positive velocity of both em ission and absorption, associated with V/R> 1. Periastron at approaching node yields V/R ~ 1 and negative shifts of emission and absorption. Weakest shell absorption in p Mon A corresponds to presentation of periastron towards the observer, since higher angular velocity then produces a minimum of density. The phase at which this occurs is consistent with an advancing periastron. According to M. Johnson (1958, Liege Symposium 7, 219), observed V/R "periods" are dynamically consistent with this hypothesis. Publication: The Astronomical Journal Pub Date: 1960 DOI: 10.1086/108122 Bibcode: 1960AJ.....65R.350M full text sources ADS |

The Be spectrum variable π Aquarii.

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Be spectrum variable π Aquarii. McLaughlin, Dean B. Abstract it Aquarii is one of the best examples of large variations of the "V/R type," in which the relative strengths of apparently double hydrogen emission lines vary in a cyclic manner. Large shifts of the emissions and the central absorption lines accompany these changes. Strongest red- ward emissions occur with greatest negative shifts of both emissions and central absorptions. Both outer edges of the emission lines shift in the sense stated, so that the absorption remains nearly central in the structure. This behavior appears to be characteristic of all the well- observed stars of this type, such as 25 Orionis (Dodson 1936), p' Monocerotis (McLaughlin 1951), and HD 20336 (McLaughlin 1958). Prior to 1924, the emission components of it Aquarii were equal, and velocities essentially constant. Then conspicuous changes began. The first cycle probably occupied four or five years (unless very rapid changes occurred in 1927 when observations were not obtained). Later cycles were two or three years in length. Velocity amplitudes reached 150 km/sec for central absorption, and 200 km/sec for edges of H~ emission. Amplitudes of both V/R and velocity were much reduced and the emission somewhat weak from 1935 to 1943. Then followed a stage of extreme weakness or absence of emission lines until 1950. After that time the emissions strengthened greatly, with nearly equal components and velocities near the mean value, - 10 km/sec. A new phase of activity began in 1956. By July, 1959, about three-fourths of a cycle had been completed and the amplitude appeared to be increasing rapidly. REFERENCES Dodson, Helen W. 1936, Ap. J. 84, i8o. McLaughlin, Dean B. 1951, A. J. 56, 44. - . 1958, A. J. 63, 51. University of Michigan Observatory Ann Arbor, Michigan Publication: The Astronomical Journal Pub Date: 1959 DOI: 10.1086/108035 Bibcode: 1959AJ.....64R.340M full text sources ADS | data products SIMBAD (2)

Shifts of Arc Lines at Various Pressures in Magnetic Fields

An investigation or certain spectral lines emitted in a high-voltage are between brass electrodes in nitrogen gas was made under pressures from 1/7 to 85 atmospheres. The arc was fun in and out of a maganetic field of 4,000 gauss. An empirical relation between the shift with and without a magnetic field at varted pressures for nine spectral lines was found. In all cases, the shift due to pressure in a magnetie field is less than in a non-magnetic field. Pressure shifts in spectral emission lines of zinc, copper, and lead in a magnetic field and in a non-magnetie field are shown graphically. (A.C.)

The Cepheid Variable S. Sagittae. II. The Emission Lines.

view Abstract Citations (16) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Cepheid Variable S. Sagittae. II. The Emission Lines. Herbig, George H. Abstract Emission components have been found in the H and K lines of the cepheid variable S Sagittae (P = 8d4, spectral type F6 Ib); they are present for 1.0-1.6 days on the rising branch of the . The bright lines are displaced shortward with respect to Fe I absorption lines by -68km/sec. Proffles have been obtained from a Mount Wilson coud plate; the lines are sharp on their longward edges, but the shortward sides are diffuse. The emission lines shift with the absorption spectrum in the pulsation cycle, and it is clear that they are not associated with the invisible component of the binary system. Intensity measurements on plates of low dispersion (53 A/mm) show that the bright K line appears about 0.6 day after minimum light, increases in strength during the time when it is present, but disappears between 0.5 and 0.9 day before maximum light. These and other facts, as well as a close parallelism with the structure and behavior of the bright Ca II lines observed in long-period variables after maximum light, indicate that the observed emissions are only the shortward wings of broad bright lines that originate low in the atmosphere of S Sagittae, the remainder being obliterated by overlying Ca ii absorption. The shortward displacement of the underlying bright line with respect to the absorption spectrum indicates that the emitting layers are rising. The observed increase of intensity of the emission may be the result of upward motion, except that the weakening of the overlying Ca II absorption line must also act to increase the observed intensity of the emission. Publication: The Astrophysical Journal Pub Date: September 1952 DOI: 10.1086/145620 Bibcode: 1952ApJ...116..369H full text sources ADS | data products SIMBAD (9) Related Materials (1) Part 1: 1952ApJ...116..348H