Laser-Enhanced Ionization Studies of the Blue Satellite Band in the Ca-Ar System Associated with the Electric-Quadrupole Transition of Calcium (original) (raw)
Lithuanian Journal of Physics, 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 configuration interaction approximation. The enhancement of theoretical intensity of quadrupole transitions by 4-6 times is obtained. It is shown that their relative intensity increases with the atomic number. In the single configuration approximation the dipole and the quadrupole transitions are separated in energy, but taking into account the configuration 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.
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.
Physical Review A, 2011
Rev. A 80, 042513 (2009)] recently reported accurate measurements on the ultraweak electric quadrupole (E2) transitions in the O 2 A band. They also presented elegant theoretical calculation of the line intensities based on Hund's case (b) formulation. However, their theoretical elucidation fails to relate to a highly relevant previous work by Balasubramanian and Narayanan [Acta Phys. Hung 74, 341 (1994)] in which closed-form expressions for the E2 branch line strengths for the eight possible rotational branches of the b 1 + g -X 3 - g transition, in intermediate coupling, are derived. The complete equivalence of the two methods is proven through direct calculation. A second point of concern is that the magnetic dipole (M1) transition moment M 1 = 0.0687 μ B deduced by Long et al. from the previously measured transition intensities is ∼2.7 times the ab initio value of 0.0255 μ B computed by Minaev et al. [Chem. Phys. 208, 299 (1996)]. Since the latter reproduces closely the measured Einstein's spontaneous emission coefficient of the A band, this large discrepancy is intriguing.
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.
Indian Journal of Physics, 2019
Energies, weighted oscillator strengths (gf), line strengths (S) and radiative rates (A) for allowed and forbidden transitions are presented for 2s2p 6 2 S 1/2-2s 2 2p 5 2 P 1/2 , 2 P 3/2 and 2s 2 2p 5 2 P 1/2-2s 2 2p 5 2 P 3/2 transitions in fluorine-like Ca XII (Z = 20), Ti XIV (Z = 22), Cr XVI (Z = 24), Fe XVIII (Z = 26) and Ni XX (Z = 28) ions. Moreover, the allowed electric dipole (E1) and the forbidden electric quadrupole (E2), octupole (E3), magnetic dipole (M1) and quadrupole (M2) transition rates for some transitions are obtained. The 2s 2 2p 5-2s 2p 6-type transitions of F-like ions are prominent in hightemperature plasmas and are useful for diagnostics. The present results are obtained from configuration interaction atomic structure calculations using the code SUPERSTRUCTURE (SS) which includes relativistic effects in Breit-Pauli approximation. The comparison of the present energies with the available observed energies displayed very good agreement (\ 1%). The presented excitation energy results have been compared with other detailed relativistic approaches such as Dirac-Fock, coupled cluster and configuration interaction for a few ionic states.
Journal of Physics: Conference Series, 2007
We have determined the amplitudes for Stark-induced (SI) transitions, of current interest in atomic physics and astrophysics, between mixed states dominated by same parity configurations of some low-lying states of singly ionized calcium. Well established Relativistic Coupled cluster (RCC) method has been used for the spectroscopic study of these transitions. This method has proved to be a very useful tool for rigorous electron correlation studies. We compare our results with experimental data for allowed electric dipole transition amplitudes and energies and also with other theoretical studies.
Annexing magic and tune-out wavelengths to the clock transitions of the alkaline-earth-metal ions
Physical Review A, 2017
We present additional magic wavelengths (λmagic) for the clock transitions in the alkaline-earth metal ions considering circular polarized light aside from our previously reported values in [J. Kaur et al., Phys. Rev. A 92, 031402(R) (2015)] for the linearly polarized light. Contributions from the vector component to the dynamic dipole polarizabilities (α d (ω)) of the atomic states associated with the clock transitions play major roles in the evaluation of these λmagic, hence facilitating in choosing circular polarization of lasers in the experiments. Moreover, the actual clock transitions in these ions are carried out among the hyperfine levels. The λmagic values in these hyperfine transitions are estimated and found to be different from λmagic for the atomic transitions due to different contributions coming from the vector and tensor part of α d (ω). Importantly, we also present λmagic values that depend only on the scalar component of α d (ω) for their uses in a specially designed trap geometry for these ions so that they can be used unambiguously among any hyperfine levels of the atomic states of the clock transitions. We also present α d (ω) values explicitly at the 1064 nm for the atomic states associated with the clock transitions which may be useful for creating "high-field seeking" traps for the above ions using the Nd:YAG laser. The tune out wavelengths at which the states would be free from the Stark shifts are also presented. Accurate values of the electric dipole matrix elements required for these studies are given and trends of electron correlation effects in determining them are also highlighted.
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.
Allowed and spin-forbidden electric dipole transitions in Ca I
Physical Review A, 2003
Energy levels, transition probabilities, and lifetimes have been determined for all levels of the Ca I spectrum up to 3d4p 1 F 3 o using the multiconfiguration Hartree-Fock method with lowest-order relativistic effects included through the Breit-Pauli Hamiltonian. The mixing of singlet and triplet configuration states was found to be considerably stronger in 4s5p 1,3 P 1 o levels than in 4s4p 1,3 P 1 o levels. The near degeneracy of the nonrelativistic 3d4p 3 F o and 1 D o term energies, differing by only 39.59 cm Ϫ1 resulted in highly mixed Breit-Pauli levels for 3d4p 3 F 2 o and 1 D 2 o. Some intercombination transitions from these levels have transition probabilities of magnitude similar to weaker spin-allowed transitions. The ''fine-tuned'' transition probability for the 4s4p 3 P 1 o-4s4d 1 D 2 transition was found to be 1.53ϫ10 3 s Ϫ1 , in agreement with a quenching rate observed in a doppler cooling experiment ͓Binnewies et al.,
American Journal of Physics, 2018
An advanced undergraduate experiment to study the 5P 3=2 ! 6P 3=2 electric quadrupole transition in rubidium atoms is presented. The experiment uses two external cavity diode lasers, one operating at the D2 rubidium resonance line and the other built with commercial parts to emit at 911 nm. The lasers produce the 5s ! 5p ! 6p excitation sequence in which the second step is the forbidden transition. Production of atoms in the 6P 3=2 state is observed by detection of the 420 nm fluorescence that results from electric dipole decay into the ground state. Lines whose widths are significantly narrower than the Doppler width are used to study the hyperfine structure of the 6P 3=2 state in rubidium. The spectra illustrate characteristics unique to electric dipole forbidden transitions, like the electric quadrupole selection rules; they are also used to show general aspects of two-color laser spectroscopy such as velocity selection and hyperfine pumping. V
Emission spectra of calcium dimer. The A u -X l Xg system
The AIX~+-X 1 + Xg spectral system of Ca 2 has been studied in two independent experiments. The collision-induced fluorescence due to this band was investigated following the resonant excitation of the 4s4p 3P 1 metastable state of calcium using a Nd : YAG laser pumped dye laser. In another experiment, a low current glow discharge in calcium vapor was used. We have assigned 86 spectral lines to this band system for vibrational quantum numbers (v'= 10-13 and v"= 0) by A X u state dissociation energy D~ is estimated to be ~ 8693.6 + 1 cm-1. The applying a Dunham type analysis. The 1 + processes involved in the collisional excitation of the upper molecular state are discussed.
The integrated intensities of the collision-induced enhancement spectra of the 2 band of CH 4 perturbed by rare gases and linear molecules (N 2 , H 2 , and CO 2 ) are calculated theoretically using the quadrupole transition moment obtained from an analysis of CH 4 -Ar spectra. In addition to the isotropic quadrupole mechanism responsible for the enhancement in CH 4 -rare gases, there is additional absorption arising from the anisotropic quadrupole mechanism in the case of molecular perturbers. This latter effect involves the matrix element of the anisotropic polarizability for the 2 transition in CH 4 that is available from the analysis of the depolarized Raman intensity measurements. Overall, the theoretical values for the slope of the enhancement spectra with respect to the perturber density are in reasonably good agreement with the experimental results, thus confirming that the collision-induced absorption arises primarily through the quadrupolar induction mechanism.