Laser-Enhanced Ionization Studies of the Blue Satellite Band in the Ca-Ar System Associated with the Electric-Quadrupole Transition of Calcium (original) (raw)
Related papers
2008
The reason of discrepancy between the experimental and the theoretical relative intensities of the 3p!2p electric quadrupole emission with respect to dipole 3s!2p emission for transition elements is investigated in relativistic conguration interaction approximation. The enhancement of theoretical intensity of quadrupole transitions by 4ñ6 times is obtained. It is shown that their relative intensity increases with the atomic number. In the single conguration approximation the dipole and the quadrupole transitions are separated in energy, but taking into account the conguration mixing their energy intervals extend and overlap. The dipole CI satellites with intensity exceeding the intensity of quadrupole transitions appear in their region, thus their separation becomes hardly possible.
Spectroscopy of forbidden transitions in ions of astrophysical interest
2003
The spectroscopic study of forbidden transitions in ions of astrophysical interest has been performed using an extension of the well-established relativistic quantum defect orbital (RQDO) method. The method has so far proved to be a very useful tool for predicting a large body of electron transition probabilities, and other related properties. The RQDO method has been applied to the study of E2 transitions in the spectra of ions relevant in astrophysics, such as Ti XII, Fe XVI, Co XVII and Ni XVIII. q
Laboratory measurements and theoretical calculations of O-2 A band electric quadrupole transitions
Physical Review A, 2009
Frequency-stabilized cavity ring-down spectroscopy was utilized to measure electric quadrupole transitions within the 16 O 2 A band, b 1 ⌺ g + ← X 3 ⌺ g − ͑0,0͒. We report quantitative measurements ͑relative uncertainties in intensity measurements from 4.4% to 11%͒ of nine ultraweak transitions in the N O, P O, R S, and T S branches with line intensities ranging from 3 ϫ 10 −30 to 2 ϫ 10 −29 cm molec. −1. A thorough discussion of relevant noise sources and uncertainties in this experiment and other cw-cavity ring-down spectrometers is given. For shortterm averaging ͑t Ͻ 100 s͒, we estimate a noise-equivalent absorption of 2.5ϫ 10 −10 cm −1 Hz −1/2. The detection limit was reduced further by co-adding up to 100 spectra to yield a minimum detectable absorption coefficient equal to 1.8ϫ 10 −11 cm −1 , corresponding to a line intensity of ϳ2.5ϫ 10 −31 cm molec. −1. We discuss calculations of electric quadrupole line positions based on a simultaneous fit of the ground and upper electronic state energies which have uncertainties Ͻ3 MHz, and we present calculations of electric quadrupole matrix elements and line intensities. The electric quadrupole line intensity calculations and measurements agreed on average to 5%, which is comparable to our average experimental uncertainty. The calculated electric quadrupole band intensity was 1.8͑1͒ ϫ 10 −27 cm molec. −1 which is equal to only ϳ8 ϫ 10 −6 of the magnetic dipole band intensity.
Physical Review A, 1991
A theory is developed to describe the spectral line shape due to interference between electric-dipoleallowed and collision-induced transitions in pure rotational molecular spectra. Motivation was provided by experimental data available for HD-inert gas systems. This theory is based on a master-equation approach to induced spectra employed by Alber and Cooper [Phys. Rev. A 33, 3084 (1986)]. The active molecule is considered to be immersed in a bath of perturbers. An expression for the absorption coeKcient is obtained within the binary collision approximation that contains terms due to allowed, induced, and interference contributions. Effects due to m mixing, J mixing, and successive collisions are included. Low-order approximations of the theory eventually reduce to results of earlier efforts, namely, the pioneering description of collisional interference by Herman, Tipping, and Poll [Phys. Rev A 20, 2006 (1979)] and refinements to it through consideration of rotational level mixing. The principal attribute of this approach is the treatment of allowed and collision-induced transitions in a consistent manner.
Spectral and electron-collision properties of atomic ions: Threshold phase shifts
Physical review, 1986
Threshold phase shifts (or equivalently, quantum defects at the series limit) are calculated within the framework of the Hartree-Slater (central-field) approximation for positive atomic ions with nuclear charge number Z & 37. The results are displayed in isoelectronic (the number of electrons, N, constant), isonuclear (Z constant), and isoionic (Z-X constant) pictures. The systematics of the threshold phase shifts are delineated, and the utility of each of the pictures is discussed. The possibilities and pitfalls of interpolation to generate new data are also discussed. This paper represents the initial report of a systematic investigation of ionic properties.
Journal of Molecular Spectroscopy, 2014
The Q(1)-Q(4) electric quadrupole transitions of the first overtone band of H 2 have been recorded for six pressure values up to 640 Torr, by CW-Cavity Ring Down Spectroscopy near 8000 cm À1. The noise equivalent absorption of the spectra is on the order of a min % 5 Â 10 À12 cm À1. Line intensities derived from a profile fit accounting for Dicke narrowing effects, range from 1.0 Â 10 À29 to 2.6 Â 10 À27 cm/molecule for the Q(4) and Q(1) line, respectively. The claimed absolute uncertainty on the derived line positions and on the line strengths are of the order of 0.001 cm À1 and 1%, respectively. The pressure line shifts of the four lines were derived allowing for an accurate determination of the position at zero pressure limit. The obtained positions and intensities agree within the experimental uncertainty with the most recent theoretical calculations including non-adiabatic, relativistic and quantum electrodynamical effects. The present frequency determinations confirm the high accuracy of these calculations. From the pressure dependence of the baseline of the CRDS spectra, the self continuum cross section of the collision induced absorption band of H 2 is determined in the vicinity of the Q(1) line. The derived cross section is found in good agreement with recent theoretical values.
Bichromatic laser-induced quadrupole-dipole collisional energy transfer in ca-sr
The journal of physical chemistry. A, 2015
We consider the response of a laser-induced quadrupole-dipole collisional system driven by a strong dressing laser field with the aim of calculating the collisional cross section of a weak inducing laser probe. The addition of a second driving field to the traditional arrangement will cause magnitude changes of the spectra and modify the profile. The calculation results show that the bichromatic laser-induced collisional energy-transfer process can be an efficient way to probe Stark splitting of both the final state and intermediate state. The magnitude and position of the splitting spectral lines are strongly dependent on the intensity of the dressing laser field. The peak cross section almost reduces by a factor of 2 with the presence of the dressing laser. Also, in the antistatic wing, bright and dark lines are periodic, appearing with the increasing of the dressing laser intensity.
Electron impact measurement of oscillator strengths for dipole-allowed transitions of atomic oxygen
Journal of Geophysical Research, 1985
Optical oscillator strengths for the seven most intense dipole-allowed transitions in the 100-eV incident energy electron scattering spectrum of atomic oxygen have been measured from forward scattering spectra. An apparatus was used in which a microwave discharge source, producing atomic oxygen seeded in a helium beam, was coupled to an electron spectrometer. The O •D population in the target beam was less than 1.5% of O 3p, and transitions from the O 3p ground electronic state only were observed. The performance of the apparatus was checked by measurement of optical oscillator strengths for helium and atomic hydrogen. Agreement with the National Bureau of Standards (NBS) values for a single spectrum of better than 10% was obtained for three He transitions and 13% for the atomic hydrogen n-3 transitions when the He I•S-2•P and H n = 1 -n = 2 Lyman series transitions were normalized to the NBS values. The atomic oxygen 2p '• 3p-2p33s 3Sø (1304 .&) transition was normalized to an average experimental value off= 0.048. Optical oscillator strengths obtained for the other transitions were 2p '• 3p-2p34s 3Sø (1040 .&), 0.010 __. 0.002; 2p '• 3p-2p33d 3Dø (1026 .&), 0.019 __. 0.001' 2p '• 3p-2p33s' 3Dø (989 .&), 0.061 +___ 0.006; 2p '• 3p-2p34d 3Dø (972 .&), 0.016 +___ 0.006' 2p '• 3p-2p33s" 3po (878 .&), 0.086 +___ 0.006; 2p,• 3p__2s2p• 3po (792 J,), 0.070 + 0.004. (All values have + 5% uncertainty in addition to the experimental scatter as indicated.) The electric dipole-forbidden transition 2p '• 3p-2p33p 3p was also observed as a weak process.
The Journal of Chemical Physics, 2001
An experimental value for the quadrupole transition moment of the 2 fundamental band of CH 4 has been determined by fitting the collision-induced enhancement spectrum of CH 4 with Ar as the perturber. The observed quadrupole-induced absorption increases linearly with the Ar density, Ar , and is comparable to the allowed dipole intensity due to Coriolis interaction with the 4 band at approximately 125 amagats. Ignoring vibration-rotation interaction and Coriolis interaction,, we equate the measured slope of the integrated intensity versus Ar to the theoretical expression for the quadrupole-induced absorption, and obtain the value ͉͗0͉Q͉ 2 ͉͘ϭ0.445 ea 0 2 for the quadrupole transition matrix element. A theoretical value ͗0͉Q͉ 2 ͘ϭ0.478 ea 0 2 has been determined by large-scale ab initio calculations and, considering both the theoretical approximations and experimental uncertainties, we regard the agreement as good, thus confirming our interpretation of the enhancement as due to the quadrupole collision-induced mechanism.