Study of coupled states for the (4s 2 ) 1 S + (4s4p) 3 P asymptote of Ca2 (original) (raw)
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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.
Theoretical study of the atomic spectra of the calcium atom
Chemical Physics Letters, 1992
Theoretical calculations are reported for the following terms of the atomic spectra of the Ca atom: ~ S (4s 2 ), l p (4s4p), 3p (4s4p), ~D(4s3d), 3D(4s3d), ~P(4s5p), 3p(4s5p). The method is based on all-electron calculations at the Hartree-Fock level followed by a configuration interaction for the two valence electrons. Core-valence (or intershell) correlation effects are introduced via a second-order perturbation development or via a core-polarization potential. The agreement with the experimental spectra is very good.
Spectroscopic characterization of excited Ca
2017
The excited Ca(4s4d DJ)RG 3 1,2 states (RG Ar, Kr, Xe have been characterized spectroscopically by R2PI resonance-enhanced two-photon ionization spectroscopy. The main vibrational progressions, assigned to Ca(4s4d D1)RG 3 1 ←Ca(4s4p 3P0)•RG 3 0 transitions, have weak subbands 3.7 0.5 cm 1 to the blue which have been assigned to analogous transitions to the 3 2 upper states. For CaAr and CaKr, rotational analysis has confirmed this assignment. The 3 2 /3 1 splitting is within experimental error the value expected if the molecular spin-orbit coupling constant is derived entirely from the Ca(4s4d DJ) atomic contribution. This indicates that there is no ‘‘heavy-atom’’ mixing of RG(nd ) character into the wave functions of the CaRG(3 ) states. © 1999 American Institute of Physics. S0021-9606 99 01526-3
Observation of the ... system of calcium dimer
We report the observation of collision-induced spectra of calcium dimer in the 680-692 nm region, The spectra were recorded after resonant laser excitation of 4 s4 P 3 PI state of atomic calcium. Here the upper state a 3 L:~ is populated through collisions, The same spectra were reproduced in a low-current glow discharge in calcium vapor. The assignment of the observed spectral lines was carried out by applying the Dunham-type analysis and the spectra were assigned to the a 3L:~-X I L:; transition of Caz, The existence of a 3L:~ state with voo = 13850 ± 1 cm-I and We ~ 37,6 cm-I is confirmed,
Laser gain is reported on the 4p3d 3F -4s3d 3D transitions of Ca at 643.907, 646.257, 647.166, and 649.378 nm following optical pumping of the 4s2 'So -4s4p 3PI intercombination transition at 657.278 nm. The effect is realized through large scale collisional redistribution of energy which rapidly leads to the excitation of higher states and eventual ionization of Ca atoms. Our calculations based on a simple rate equation model suggest that population inversions are a combined result of direct excitation of the upper lasing states through inelastic collisions, and three-body recombination.
Experimental study of the Ca2 {1}S+ {1}S asymptote
European Physical Journal D, 2003
The van der Waals coefficients C6, C8 and C{10} at the ^1S+^1S calcium dimer asymptote are determined from spectroscopic observations. The filtered laser excitation technique was applied for measuring transition frequencies of the Ca2 B-X system from asymptotic levels of the X^1Σ_g+ ground state reaching v''=38. That level which is only 0.2 cm^{-1} below the molecular ^1S+^1S asymptote has an outer classical turning point of about 20 Å. The extraction of confidence limits for the long range coefficients including the dissociation energy from the experimental data involving Monte Carlo simulation is described. A range for the s-wave scattering length is derived.
Evidence for a non-Rydberg molecular doubly excited state of Ca2
Chemical Physics Letters, 2009
We report experimental and theoretical evidence of a non-Rydberg molecular doubly excited state of Ca 2 involving excited molecular orbitals mixing 4p and 3d characters. The excitation spectrum of Ca 2 , carried by helium or argon clusters, is recorded experimentally in the range 25600-27800 cm −1 , displaying a bimodal structure. The latter is interpreted from ab initio calculation and analysis of the adiabatic states of Ca 2 up to doubly excited asymptotes Ca(4p3d 1 D)+Ca(4s 2 1 S) and Ca(4s3d 3 D)+Ca(4s4p 3 P), and the relevant dipole transition moments. The bimodal structure is assigned as resulting from the avoided crossing between adiabatic states 3 1 Π u and 4 1 Π u , reflecting the mixing of doubly excited configurations and absorbing singly excited configurations.
Physical Review A, 1997
In this work the autoionization of the configuration Ca 3p 5 3d4s4 p of free calcium atoms has been investigated by the use of angle-resolved photoelectron spectroscopy. In a first step, atoms in the ground-state Ca 3p 6 4s 2 1 S 0 were laser excited and aligned to the first optically excited-state Ca 3p 6 4s4p 1 P 1 . From this intermediate state, with the help of synchrotron radiation ͑31.5-34.5 eV͒, the closed 3 p subshell was opened, leading to the population of Ca 3 p 5 3d4s4 p autoionizing states. The autoionization decay of these states to both the ground state and shakeup states of singly charged ions was investigated using two types of photoelectron spectrometers. An angle-integrating spectrometer allowed us to tentatively assign the dominating angular momenta and to measure the relative partial cross sections. Furthermore, by combination with an angle-resolving spectrometer the angle dependence of the outgoing photoelectrons in the region of 32.7-33.3 eV was completely characterized for the three main diagram lines. Completeness was achieved in the sense that for action of linearly polarized light sources maximal information was extracted.
The Journal of Physical Chemistry A, 2006
The Ca * +CH 3 F → CaF * +CH 3 reaction was photoinduced in 1:1 Ca · · · CH 3 F complexes formed in a supersonic expansion. The transition state of the reaction was explored by monitoring the electronically excited product, CaF, while scanning the laser that turns on the reaction. Moreover, the electronic structure of the Ca · · · FCH 3 system was studied using ab-initio methods by associating a pseudopotential description of the [Ca 2+ ] and [F 7+ ] cores, a core polarization operator on calcium, an extensive Gaussian basis and a treatment of the electronic problem at the CCSD(T) (ground state) and RSPT2 (excited states) level. In this contribution we present experimental results for the free complex and a comparison with the results of a previous experiment where the Ca · · · CH 3 F complexes are deposited at the surface of large argon clusters. The ab-initio calculations allowed an interpretation of the experimental data in terms of two reaction mechanisms, one involving a partial charge transfer state, the other involving the excitation of the C-F stretch in the CH 3 F moiety prior to charge transfer.