A. Bernard

The 5d states of barium hydride; BaH and BaD

The A′2Δ, A 2Π and B 2Σ+ states of BaH and BaD which correlate with Ba …6s5d 3D have been observed in infra-red laser-induced fluorescence from E 2Π and in thermal emission to the ground state, X 2Σ+. The spectra were recorded interferometrically using a high resolution Fourier transform spectrometer. Observations include v = 0 and 1 of the complex, both for BaH and BaD. A global analysis of these levels is given in terms of an effective hamiltonian for a d-complex. The observed interactions require a 15 × 15 representation of the complex of BaH, with the use of experimental data for v = 2 taken from the work of other authors. However an independent 5 × 5 representation of each vibrational level is shown to describe the BaD spectrum with very good accuracy, in particular the complicated local A′2Δ ∼ A 2Π perturbations. The spectra of both molecules are reproduced to within the experimental precision. Deperturbed energies and rotational constants, and values of the interaction constants are given. A consis...

Studies of the electronic states of the BaF molecule

Laser-excited fluorescence and thermal emission spectra, recorded at high resolution by Fourier-transform spectrometry, have been analysed to yield new information about the ground-state, X2Σ+, and six of the lowest-lying electronic states of BaF. In the present paper we give values of the effective constants for X2Σ+, A′2Δ, A 2Π, B 2Σ+, C 2Π, D 2Σ+ and F 2Π derived from an overall simultaneous fit to some 6470 lines assigned to rotational structure of 24 bands of 10 systems. Existing analyses are confirmed and extended, and a rotational analysis of levels of the state C 2Π is given for the first time: the spin-orbit coupling constant in this state is found to increase unexpectedly rapidly with increasing v. The states A′2Δ, A 2Π and B 2Σ+ interact strongly, and their mutual deperturbation, and the determination of their interaction constants form the subject of the following paper (Part II).

Studies of the electronic states of the BaF molecule: Part II: The 5d(v= 0, 1, 2) states

Obtention des energies deperturbees et des constantes rotationnelles pour les niveaux v=0, 1, et 2 des etats sd. Determination des valeurs des constantes dinteraction spin-orbite et rotationnelles

The metastable A′ 2Δ state of BaF

Abstract Absorption of Ar + laser lines in the C 2 Π-X 2 Σ + system of BaF leads to infrared fluorescence, C 2 Π-A′ 2 Δ. This has been recorded at high resolution by Fourier-transform spectrometry. Constants for the 2 Δ state have been determined, and some improvements in the values of the constants for X 2 Σ + , B 2 Σ + and C 2 Π are also reported.

The 5d complex of barium hydride; BaH and BaD

The metastable 2Δ states of BaH and BaD have been identified in laser-induced fluorescence and chemiluminescence spectra. Together with the known states A 2Π and B 2Σ+, the 2Δ states form a group of interacting components, and the analysis is given of the v = 0 levels in terms of an effective hamiltonian for a d-complex. Deperturbed energies, rotational constants and values of the interaction constants are given.

Electronic structure of BaLi. II. First observation of the Ba6,7Li spectrum: Analysis of the (2)2Π→X 2Σ+ system

The thermal emission at high temperature (1100u2009°C) of BaLi has been analyzed spectroscopically at high resolution with a Fourier transform spectrometer. Molecular emission in the infrared region is observed and is ascribed to a transition from the (2)2Π state towards the ground state Xu20092Σ+ of BaLi. These states (among several others) have been predicted from ab initio calculations [see part I, A. R. Allouche and M. Aubert‐Frecon, J. Chem. Phys. 100, 938 (1994)]. Very good agreement is observed between theoretical predictions and experiment for the energy of the (2)2Π state and spectroscopic constants of both states. Both isotopic species Ba7Li and Ba6Li have been investigated and molecular parameters are derived from the analysis of the (2)2Π→Xu20092Σ+(0,0) band (the one analyzable band). No irregularities appear in the rotational structure.

The H 2Δ state of barium hydride

Using a tunable laser to excite the E2 Pi -X2 Sigma + system of the BaH molecule, the authors recorded (with the help of a Fourier transform spectrometer) and analysed the fluorescence induced in both the visible and infrared regions. This was found to correspond to the E2 Pi -X2 Sigma , E2 Pi 3/2-A2 Pi 3/2,E2 Pi -B2 Sigma + and E2 Pi 3/2-H2 Delta 5/2 transitions. So the H 2 Delta state previously identified from perturbations affecting the A 2 Pi levels is directly observed for the first time. A consistent set of effective molecular constants is derived for the Omega =5/2 component of the H state from the simultaneous reduction of the wavenumbers of 164 regular lines in the E-X (0-0) band and E-H (0-0) and (0-1) sub-bands. A noticeable Lambda -type doubling occurs in H 4 Delta 5/2 levels. The constants found are (cm-1): T5/2 =9424.79 (2) ( nu = 0) and 10 497.08 (10) ( nu =1); B5/2= 3.1189 (2) ( nu =0)and 3.0569 (6) ( nu =1); and D5/2=0.89 (1)*10-4 ( nu =0) and 0.9*10-4 ( nu =1). The energies T5/2 ( nu =0, 1) refer to the level X 2 Sigma ( nu =0, N=0).

Laser-induced fluorescence of CaF: the B' 2 Delta state

The 3375 AA line of a krypton ion laser has been used to excite red and near infrared fluorescence, recorded by Fourier-transform spectrometry, in CaF. The main transition pumped is R1(2.5 e) in the 0-1 band of C 2 Pi -X 2 Sigma +. Lines of three systems have been measured: C 2 Pi 12/-A 2 Pi 12/, C 2 Pi 12/-B 2 Sigma + and C 2 Pi 12/-B 2 Delta 32/. T00(2 Delta 32/) is about 21530.8 cm-1, and the effective value of B0 for the same level is 0.32357 (13) cm-1.

Spin–orbit interaction between c 3Σ+ and B 1Π states of ScF: Effects on the fine and hyperfine structures

The introduction of an off‐diagonal spin–orbit interaction element in the Hamiltonian matrix representing the close‐lying Bu20091Π and cu20093Σ+ states of ScF allows us to interpret the anomalies previously observed, i.e., the large Λ‐type doubling in Bu20091Π and the large spin‐splitting in cu20093Σ+ at v=0, both of which decrease rapidly with increasing vibration. Deperturbed molecular constants for the v=0,1,2 levels in both states, together with values of the interaction parameter, are obtained from the numerical treatment of the wave numbers of 1454 lines in the Bu20091Π→Xu20091Σ+(0‐1), (1‐1), (2‐0), (2‐2), and cu20093Σ+→Xu20091Σ+(0‐1), (1‐0), (2‐0) bands. The interaction between Bu20091Π and cu20093Σ+ is greatest at v=0 and decreases rapidly with increasing v. The model of the states including hyperfine effects is then used to interpret the observed hyperfine structure which is attributed to strong interaction between the 4sσ3dσ electrons and the 45Sc nucleus of spin 7/2. The hyperfine structure of the rotational levels in Bu20091Π(v=0,1,2) a...

Characterization of the B(1) 1Π state of scandium monochloride

Laser-induced fluorescent lines in the (3) 1Π to B(1) 1Π (0-0) and (1-1) bands of scandium monochloride are observed spectroscopically for both isotopomers, 45Sc35Cl and 45Sc37Cl. Rotational analysis of the spectra allows the characterization of the B(1) 1Π state. Preliminary values of the principal constants at equilibrium in this state for 45Sc35Cl are, in cm-1: Te = 6020.3, ΔG1/2 = 379.1, Be = 0.1551.