Pressure-scanned Fabry-Perot Interferometer Research Articles

Thermalization of sputtered aluminium atoms in an electron cyclotron resonance plasma source

The transverse temperature of sputtered aluminium atoms in an electron cyclotron resonance discharge has been calculated from the shapes of their Doppler broadening emission lines, which were measured with a pressure scanning Fabry–Perot interferometer. This temperature decreases from 0.8 to 0.28 eV at a distance of 17.5 cm from the Al target when krypton pressure rises from 0.4 to 4 mTorr. For a discharge in argon aluminium temperature falls from 0.5 to 0.18 eV for the same condition.

Experimental study of speed-dependent collisional effects of He and Ne on the 687.1 nm argon line

Using a pressure-scanned Fabry-Perot interferometer precise measurements of the profiles of the 687.1 nm argon line perturbed by helium and neon pressures between 0.5 and 44 torr have been performed. Careful analysis of line shapes showed that for Ar-He the speed-dependent effects do not play any essential role. Contrary to that, for Ar-Ne these effects can give rise to noticeable decrease of the Doppler width determined using the Voigt profile. It was shown that for Ar-Ne the inclusion of speed-dependent effects can reduce the apparent dependence of the Doppler width on the neon density and cause the Doppler temperatures determined from the profiles to be consistent with the source temperature. The role of the Dicke narrowing is also discussed.

Influence of krypton on the shape and shift of the 326.1 nm (51 S0 –53P1) Cd intercombination line

The collisional broadening and shift of the 114Cd 326.1 nm (5 1S0-5 3P1) intercombination line perturbed by Kr have been investigated using a pressure-scanned Fabry-Perot interferometer. The values of pressure broadening and shift coefficients determined from experiment are compared with those calculated on the basis of the classical Lindholm-Foley impact theory for van der Waals, Lennard-Jones, Morse and Czuchaj-Sienkiewicz potentials.

Low pressure broadening and shift of the cadmium intercombination line 326.1 nm (5 1S0-5 3P1) perturbed by He and Ne

The collisional broadening and shift of the 114Cd intercombination line lambda =326.1 nm (5 1S0-5 3P1) perturbed by He and Ne have been investigated using a pressure-scanned Fabry-Perot interferometer. The values of pressure broadening and shift coefficients determined from the experiment compared with those calculated by Czuchaj and Sienkiewicz (1987) and with values resulting from the Lennard-Jones potential.

Optical interferometer measurements of thermospheric temperature at Kavalur (12.5°N, 78.5°E), India

First results on the behaviour of thermospheric temperature over Kavalur (12.5°N, 78.5°E geographic; 2.8°N geomagnetic latitude) located close to the geomagnetic equator in the Indian zone are presented. The results are based on measurements of the Doppler width of O( 1D) night airglow emission at 630 nm made with a pressure-scanned Fabry-Perot interferometer (FPI) on 16 nights during March April 1992. The average nighttime (2130-0430 IST) thermospheric temperature is found to be consistently higher than the MSIS-86 predictions on all but one of the nights. The mean difference between the observed nightly temperatures and model values is 269 K with a standard error of 91 K. On one of the nights (9/10 April 1992, Ap = 6) the temperature is found to increase by ~250 K around 2330 IST and is accompanied by a ‘midnight collapse’ of the F-region over Ahmedabad (23°N, 72°E, dip 26.3°N). This relationship between the temperature increase at Kavalur and F-region height decrease at Ahmedabad is also seen in the average behaviour of the two parameters. The temperature enhancement at Kavalur is interpreted as the signature of the equatorial midnight temperature maximum (MTM) and the descent of the F-region over Ahmedabad as the effect of the poleward neutral winds associated with the MTM.

Broadening and shift of the resonance line of thallium due to collisions with neon and argon atoms

The width and shift of the resonance line of thallium ( lambda =377.68 nm) perturbed by neon and argon were investigated at low perturber densities using a pressure-scanned Fabry-Perot interferometer. The results are compared with those calculated on the basis of the van der Waals, Lennard-Jones and Czuchaj-Sienkiewicz potentials. Results obtained from this experiment are compared with data reported previously for this line and for other transitions in thallium.

Pressure effects of krypton and xenon on the 535 nm thallium line

The shape and shift of the 535 nm thallium line perturbed by krypton and xenon were investigated at low densities using a pressure-scanned Fabry-Perot interferometer. The linear dependence of both the Lorentzian halfwidth and the shift on the perturbing gas density was found. Our results are compared with the previous experimental data obtained by different methods as well as with the theoretical ones.

Pressure Effects of Neon and Argon on the 535 nm Thallium Line

Experimental studies of collisional broadening and shift of the 535 nm thallium line perturbed by neon and argon were performed using a pressure-scanned Fabry-Perot interferometer. The 535 nm line was excited by irradiation of the thallium vapour with the resonance thallium line (377.68 nm). The present results are compared with previous experimental data obtained by different methods as well as with theoretical ones.

Isotope shift and hyperfine structure in low-lying levels of molybdenum

Isotope shifts and hyperfine structure in four transitions of Mo have been measured with a pressure-scanning Fabry-Perot interferometer. The isotope shifts have been combined with all other known isotope shifts in transitions connecting the 4d55s7S and5S and 4d45s25D levels with the 4d55p5P and7P levels in a multidimensional King plot. Values of delta (r2) from muonic-atom isotope shifts are used to separate mass and field shifts, giving improved values of delta (r2) for the isotope pairs, A, A'.

Observations on metastable neon atoms in hollow-cathode discharges

Previous work on the intensity versus current relationship for Ne l spectral lines emitted by iron hollow-cathode lamps with neon as the carrier gas has been extended. Spectral line profiles have been recorded with a pressure scanning Fabry-Perot interferometer. Lines corresponding to transitions to the metastable state 3s[3/2]02 exhibit self-reversal and broadening due to self-absorption. This indicates the existence of a high density of neon atoms in this state, which is the likely intermediate level in two-step excitation processes.

Observation of spectral line profiles emitted by an inductively coupled plasma—I.: On the wavelength shift of spectral lines

Profiles of 16 spectral lines stemming from 8 elements (Ar, Na, Cu, Sr, Cd, Ba, Mg and Li) emitted by an inductively coupled plasma (ICP) have been observed and measured with a pressure-scanning Fabry-Perot interferometer. In the process of profile observations, we have found wavelength shifts of spectral lines in an ICP and for the first time studied this phenomenon quantitatively and systematically in a spectrochemical source. The profiles of spectral lines emitted by the ICP have been compared with those emitted by hollow cathode lamps. The magnitude of the wavelength shift to the red or the blue varied more or less with the plasma conditions, observation position and the concentration of a concomitant, cesium. In the present work the observed line profiles were not deconvoluted for the apparatus profiles. Typically the order of magnitude of the wavelength shift measured for spectral lines that show large shifts at an observation height of about 4 mm in an “analytical” ICP is n × 10 −3 nm, where n is about 4 for Ar I 427.2 nm and about 1 for Cu I 521.8 nm and Sr II 430.5 nm. With regard to the wavelength shift, several trends and/or regularities were found. The Stark effect is considered as the main cause of the phenomena.

Ring nebulae associated with Wolf-Rayet stars in the Large Magellanic Cloud. II - Kinematics of DEM 45, 137, 165, 174, and 208

view Abstract Citations (11) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ring nebulae associated with Wolf-Rayet stars in the Large Magellanic Cloud. II - Kinematics of DEM 45, 137, 165, 174, and 208 Chu, Y. -H. Abstract The velocity fields of five ring nebulae associated with Wolf-Rayet stars in the Large Magellanic Cloud are investigated in order to distinguish among possible origins. Velocities were mapped by the use of the CTIO pressure-scanned Fabry-Perot interferometer at the forbidden O III line, and the high-resolution line profiles obtained were used to determine the dynamical ages of the nebulae. Comparison of ring dynamical ages with the age of the Wolf-Rayet star confirms DEM 174 as an amorphous H II region illuminated by the star. DEM 45 and 165 have internal motion less than 10 km/sec, while DEM 137 and 208 are shells expanding at about 15 to 20 km/sec with dynamical ages of several million years. These last four are structured H II regions, and are 10 to 20 times larger than their Galactic counterparts. It is suggested that the two largest rings, DEM 137 and 208, were formed by stellar associations, while DEM 45 and 165 are part of a molecular cloud-H II region complex. Publication: The Astrophysical Journal Pub Date: April 1982 DOI: 10.1086/159805 Bibcode: 1982ApJ...255...79C Keywords: Hydrogen Ions; Magellanic Clouds; Nebulae; Wolf-Rayet Stars; Amorphous Materials; Fabry-Perot Interferometers; Forbidden Transitions; H Ii Regions; High Resolution; Astronomy full text sources ADS | data products NED (1)

A long path Jamin interferometer for monitoring pressure scanned Fabry-Perot interferometers

A refined method for the reduction of the signal-to-noise ratio in pressure-scanned Fabry-Perot interferometer measurements is described. This is achieved by phase-correct superposition of the individual interference orders. By adding a specially developed Jamin-type pressure scanning interferometer with a large effective light path length of 10 m (which results in a number of pressure marks as high as about 8800 between vacuum and atmospheric pressure) the pressure measuring and averaging process is much more exact than in former set-ups. At a wavelength of 632.8 nm for the light to be analyzed by the Fabry-Perot interferometer, the interval between two pressure marks then corresponds to 15 MHz. This makes the instrument also suitable for the control of a pressure scanned tunable dye laser.

Wavelength Measurement of an H2CO-Stabilized He-Xe Laser at 3.51 µm

The vacuum wavelength of an H2CO (51,5(ground state)→60,6(v5=1))-stabilized He-Xe laser was measured with respect to the CH4-stabilized He-Ne laser at 3.39 µm by using a pressure-scanning Fabry-Perot interferometer. The average value λ̄H2CO of the vacuum wavelength obtained was 3 507 979.48 pm. The standard deviation σn-1 was 0.39 pm with an accuracy of σn-1/λ̄H2CO=1.1×10-7. The estimated values of the systematic errors were -0.24 pm≦ΔλH2CO,1≦0, ΔλH2CO,2=0.004 pm, and ΔλH2CO,3=0.02 pm, respectively, where ΔλH2CO,1, ΔλH2CO,2, and ΔλH2CO,3 represent the errors caused by diffraction, nonparallelism between the interferometer mirrors, and nonparallelism between the two laser beams, respectively.

Depolarized light scattering from shear waves in aniline and quinoline*

The spectrum of depolarized light scattered at 90° from aniline and quinoline was analyzed near the exciting frequency in order to determine the frequencies of thermal shear waves that exist in the liquids as a function of temperature. The light source was a multimode He-Ne laser and the analyzing instrument was a pressure scanned Fabry–Perot interferometer. The results of the investigation indicate that the shear wave frequency rises with temperature in the vicinity of room temperature.

Extended measurements of isotope shifts in Mg I

The isotope shifts in the Mg I transitionsλ 2,852 A (3s 2 1 S 0-3s3p 1 p 1 P 1) andλλ 3,829, 3,832 and 3,838 A (3s3p 3 P-3s3d 3 D) have been measured for24Mg,25Mg and26Mg. The measurements were carried out using a pressure scanned Fabry-Perot interferometer and separated isotopes excited in hollow cathode discharge tubes. The results are compared to theoretical predictions and an attempt is made to convert measured line shifts into level shifts.

Absolute Wavelength Measurements of the Iodine 127 Stabilized He-Ne Laser of NRLM

Absolute wavelength measurements of the 127I2 stabilized He-Ne laser of NRLM have been made by comparison with the 86Kr primary standard using a pressure scanning Fabry-Perot interferometer. Vacuum wavelength value is given for the i-component of 127I2. The wavelength value obtained is 632991399.95 fm with a standard error of 3 × 10-9. This agrees with the value recommended by CCDM(632991399 fm) within 2 × 10-9.

Interferometric studies of the twilight and nightglow sodium D-line profiles

A 150 mm aperture, pressure scanned Fabry-Perot interferometer has been used to study the midlatitude twilight and nightglow sodium D-line profiles. The line width measurements during evening and morning twilight indicate that the sodium layer temperature rises to a midwinter maximum (∼230 K) and then falls to a midsummer minimum (∼150 K), in qualitative agreement with the CIRA 1972 model predictions. Nightglow intensity measurements obtained with the interferometer indicate a highly variable behaviour, ranging from near-constant intensities, to monotonically falling, and to rising and falling intensities during the night. Broadening of the nightglow line profiles yields a sodium atom dissociation kinetic energy of (46 ± 4) meV. This suggests that the Chapman NaO + O chemiexcitation process, rather than dissociative recombination of “corkscrewing” ions and electrons, gives rise to the nightglow.

Digital normalization of iodine filter structure in quasielastic light scattering

A molecular iodine filter may be used to reduce the elastic component in a light scattering experiment by several orders of magnitude. However, this introduces extraneous structure into the spectrum due to subsidiary iodine absorptions. A technique is reported here to compensate quantitatively for this structure by a digital normalization scheme based upon a tandem pressure-scanned Fabry-Perot interferometer interfaced to a minicomputer. This technique has allowed the extraction of quantitative line-shape information in studies of low-energy (0–3.0 cm−1) excitations in both crystalline and amorphous solids.

Collisional broadening and shift of neutral argon spectral lines

The collisional self-broadening and shift of neutral argon spectral lines have been determined as a function of atom density $N$ for several lines terminating on either the lower resonance or lower metastable levels. The lines were emitted by a variable-pressure discharge tube equipped with intracapillary thermocouples, and were observed using a pressure-scanned Fabry-Perot interferometer. The line profiles were analyzed using a least-squares fit of Whiting's Voigt function to all profile intensity points. Particular attention was given to the determination of the gas temperature, from which $N$ was calculated. The contribution of nonresonant interactions to the broadening and shift of lines connected to the ground state via resonant transitions was examined using the analysis of Lewis.