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Several new states of Li2have been observed in fluorescence, excited by Ar+, Kr+and cw dye lasers. Results from the analysis of high resolution Fourier transform spectra are reviewed, and spectroscopic constants are compared with ab initio predictions.

In this article the 11Σ+electronic ground state is studied up to near the dissociation limit. Calculations have been carried out using previous experimental data and taking into account the exchange energy that cannot be neglected. In this calculations, new values for the multipolar van der Waals coefficients Cnhave been obtained showing a good agreement with the previous theoretical ones.

The emission spectrum of a platinum hollow cathode lamp has been recently recorded by means of a grating spectrograph at the National Institute of Standards and Technology (N.I.S.T.) and by Fourier transform spectrometry at Kitt Peak National Observatory and at Laboratoire Aimé Cotton. The classification of Pt I lines is revised and extended. One hundred-nineteen new energy levels have been added to the 83 earlier ones, four of which are assigned revised J-values. Seventy percent of the levels are interpreted theoretically by means of Slater-Condon type calculations of (5d + 6s)10, 5d96d, 5d97s, 5d97d, 5d98s and (5d96p + 5d86s6p + 5d76s26p + 5d97p). The ionisation limit 5d92D5/2at $72~230\pm 50$cm-1(8.956±0.006 eV) has been derived from 5d9ns, 5d96f and 5d86s5f levels.

In this work, the BaI D2Σ+and G2Σ+electronic states were investigated using laser-induced fluorescence (LIF) and Fourier transform spectroscopy (FTS). The LIF visible spectra were obtained by using the second harmonic of the Ti:sapphire single-mode laser and the Ar+and Kr+multimode lasers as excitation sources. Previously recorded data, taken from C. A. Leach, A. A. Tsekouras, and R. N. Zare (1992, J. Mol. Spectrosc. 153, 59–72) and from R. F. Gutterres, J. Vergès, and C. Amiot (1999, J. Mol. Spectrosc. 196, 29–44; 2000, J. Mol. Spectrosc. 200, 253–260; and 2000, J. Mol. Spectrosc. 201, 326–327) were combined with the present data. Accurate and improved molecular constants for the X2Σ+, B2Σ+, A′2Δ, A2Π, C2Π, and D2Σ+states and 16 term values of the G2Σ+state were derived from a simultaneous treatment of the whole data set (12 684 transitions) with a standard deviation of 3.26×10−3cm−1.

Rotational analyses of 32 subbands of the near-infrared 3Φ → (1)3Δ system of LaF have been carried out, involving the levels v= 0–7 of the two states. The three subsystems were first treated as separate singlet systems, directly at equilibrium. Perturbations were revealed in the lower state, ascribed to spin–uncoupling interactions between (1)3Δ3(v) and (1)3Δ2(v+ 1) levels. A 21 × 21 matrix representation at equilibrium of the complex of interacting levels (v= 0–6) was then constructed, each diagonal v-block corresponding to a triplet model of the rovibrational 3Δ Hamiltonian. The observed perturbations were completely reduced in the harmonic oscillator approximation with an experimental value of the interaction parameter BΔ0,1= 0.01322(2) cm−1. The wavenumbers of some 4500 lines of the system were fitted with an rms error of about 0.005 cm−1. (Line lists are available in electronic form via http://www-obs.univ-lyon1.fr/~ABernard/index.html.)

The E2Σ+→ C2Π Rydberg–Rydberg transition of 14N16O near 8492 cm−1has been studied by Fourier transform spectrometry in the emission from a dc excited supersonic jet expansion and from a dc discharge under equilibrium conditions. The same transition has also been observed in laser-induced stimulated emission. Line wavenumbers of the 0–0, 1–1, and 2–2 bands, together with data for previously published near-infrared transitions, have been reduced to consistent sets of rovibronic term values for v= 0, 1, and 2 of the A2Σ+, D2Σ+, E2Σ+, and C2Π states which frequently serve as intermediates in the multiphoton excitation of higher Rydberg levels of NO.

Near-infrared and visible spectra of the A2Π–X2Σ+, C2Π1/2–A2Π1/2, C2Π1/2–B2Σ+, and C2Π1/2–X2Σ+band systems of the BaI molecule were recorded by using Fourier transform spectroscopy (FTS). The spectra were produced from the chemiluminescent reaction Ba + I2and also by using laser-induced fluorescence (LIF) technique in which the laser sources were a Ti:sapphire single-mode laser, a dye single-mode laser, and a Kr+multimode ion laser. Resolved rotational data, originating from 19 vibrational levels (0 ≤ v≤ 5 and 7 ≤ v≤ 19) of the A2Π state, 24 vibrational levels (0 ≤ v≤ 18 and 20 ≤ v≤ 24) of the X2Σ+state, and 8 vibrational levels (1 ≤ v≤ 2 and 9 ≤ v≤ 14) of the C2Π state, were used in the final analysis. Previously recorded data for the B2Σ+–X2Σ+and C2Π–X2Σ+systems, taken from R. F. Gutterres, J. Vergès, and C. Amiot, J. Mol. Spectrosc.196, 29–44 (1999) and from C. A. Leach, A. A. Tsekouras, and R. N. Zare, J. Mol. Spectrosc.153, 59–72 (1992), were added to the present work data field. Accurate and improved molecular constants, for the X2Σ+, B2Σ+, A2Π, and C2Π states, were derived from a simultaneous treatment of the whole data set.

In this paper a new spectroscopic investigation on the X1Σ+electronic ground state of the RbCs molecule is reported. This study is conducted by using laser-induced fluorescence combined with Fourier transform spectroscopy (LIF–FTS). More than 23000 spectral data are used in a global linear reduction to molecular constants. With these new and improved molecular constants, the potential energy curve has been calculated by the inverted perturbation approach (IPA). Accurate values for the dissociation energy and the long-range parameters have been derived.

The near-infrared spectrum of the B2Σ+–X2Σ+band system of the BaI molecule, obtained from the chemiluminescent reaction Ba + I2and also by laser-induced fluorescence (LIF), was recorded by using Fourier transform spectroscopy (FTS). The LIF spectra were obtained by using a Ti:sapphire single-mode laser excitation. Resolved rotational data, originating from 32 vibrational levels (0 ≤ v≤ 31) in the X2Σ+state and from 24 vibrational levels (0 ≤ v≤ 19, and v= 21, 22, 23, 26) in the B2Σ+state, were used in the final analysis. Previously recorded data for the C2Π–X2Σ+band system (with Δv= 0), taken from C. A. Leach, A. A. Tsekouras, and R. N. Zare, J. Mol. Spectrosc.153, 59–72 (1992), were added to the present work data field. Accurate and improved molecular constants for the X2Σ+, B2Σ+, and C2Π states were derived from a simultaneous treatment of the whole data set.

An extensive study of theB(1)1Π →X1Σ+system of45Sc35Cl and45Sc37Cl observed in high resolution spectra of the molecular thermal emission is presented. The rotational analysis reveals the presence of localized perturbations in almost all branches of bands withv′ ≤ 5, associated with hyperfine broadening of the perturbedQlines. These effects are interpreted as consequences of the avoided crossing betweenB(1)1Π(v) and (1)3Σ+(v+ 2) levels due to spin–orbit interaction. It appears possible to enter the interacting levels for both isotopomers in the same matrix representation, the energy term elements only involving equilibrium parameters of the states (isotopically scaled to45Sc35Cl). A semideperturbed model of the interacting states, taking account of the (v∼v+ 2) perturbations only, is first envisaged. The simultaneous fit of some 6600 line wavenumbers in 17 bands for45Sc35Cl and 7 bands for45Sc37Cl with a total standard deviation of 0.005 cm−1makes it possible to characterize the (1)3Σ+state and precisely describeB(1)1Π fromv= 0 tov= 5. Spin–orbit interaction parameters ξv,v+2are determined. A full deperturbation is then carried out using a model describing the levelsv= 0 tov= 7 of45Sc35Cl andv= 0 tov= 4 of45Sc37Cl for the two states, and taking account of all significant interactions. The following principal equilibrium molecular constants (in cm−1) are obtained: —for (1)3Σ+,[formula]The vibration-independent spin–orbit interaction parameter is directly determined, ξel= 53.02 cm−1.

The emission spectrum of ^209Bi has been observed in the infrared region using a Fourier-transform spectrometer at Laboratoire Aimé Cotton, Orsay, using a microwave-excited discharge tube as the light source. In this paper, we report the identification of the 5ƒ–;5g, 5ƒ–;6g, 5ƒ–;7g, and 5ƒ–;8g transitions. We have also located the 6d–;5ƒ, 6d–; 6ƒ, 6d–;7ƒ, 6d–;8ƒ, 6d–;9ƒ, 7d–;6ƒ, 7d–;7ƒ, 7d–;8ƒ, and 7d–;9ƒ transitions. Using the ƒ–g transitions, we have recalculated the ionization limit of bismuth to be 58 760 ± 1 cm^−1.

The spectrum of neutral bismuth has been studied in the infrared region by means of the Fourier-transform spectrometer at the Laboratoire Aimé Cotton, Orsay, France. A microwave-excited discharge tube containing bismuth iodide was used as the light source. A total of 37 hyperfine structures was studied. Precise measurements of the center of gravity of the structures give energy levels with an error less than 0.005 cm^−1. Complete analysis of these hyperfine structures resulted in the determination of the magnetic-dipole and the electric-quadrupole interaction constants for 10 even and 12 odd levels. The present results have increased the number of newly classified lines to 78, as compared with 28 reported in our earlier work [ J. Opt. Soc. Am.72, 589 ( 1982)]. The analysis has also resulted in the confirmation and the assignment of many J values, improved values of energy levels, and two new levels.

New uranium hollow-cathode Fourier-transform spectra have been recorded between 1800 and 42 000 cm^-1. Combined with earlier visible and ultraviolet spectra, these have led to 354 odd levels and 809 even levels of singly ionized uranium (U II) belonging to four odd and six even configurations. High-resolution Fourier-transform spectra of an electrodeless discharge lamp containing ^238UI_4 and ^234UI_4 were used to measure splittings of more than 800 isotopic U II doublets to an accuracy of ~0.001 cm^-1. From these transition isotope shifts 114 odd- and 397 even-level isotope shifts were determined.

Rotational analyses have been carried out on eight thermically excited emission bands of the infraredB1Π → X1Σ+system of scandium monoiodide between 4000 to 5000 cm−1, recorded by Fourier transform spectrometry. Rotational constants and energies are obtained forX1Σ+(v= 0, 1, 2) andB1Π (v= 0–4) levels from which equilibrium constants of the states are derived. Perturbational effects are observed in the bands withv″ = 1 that are interpreted as consequences of the avoided crossing ofX1Σ+(v= 1) anda3Δ1(v= 0) atJ= 70. A treatment of the perturbation is made using an effective 2 × 2 matrix representation of the rotational energies of the two levels.

The spectrum of neutral ^121Sb emitted by an electrodeless discharge lamp has been observed in the range 2 536–24 786 cm^−1. The wavelengths of 617 lines have been measured. The hyperfine-structure splitting factors of the levels were established for 77% of these lines. Thirty-two new energy levels were found, and several J values were revised. The Slater–Condon method was used for the interpretation of levels in both parities, and the multiconfiguration eigenfunctions were applied to the parametric study of the hyperfine-structure factors A and B. The multichannel quantum-defect theory analysis of high odd levels having J = 1/2 and J = 3/2 was also revised.

We have measured 6096 Np wavelengths with the 9 m Paschen-Runge spectrograph at Argonne and the Fourier transform facilities at Aime Cotton, of which 40% have been classified as transitions between 130 even levels and 329 odd levels. Most of the even levels and half of the odd levels have been identified by hyperfine structure and Zeeman data. The ground configuration is 5ƒ^46d7S^2; the next configuration, 5ƒ^57s^2, starts at 2831 cm^-1. The low levels of 5ƒ^46d^27s, 5ƒ^36d^27s^2 , and 5ƒ^46d7s7p have been identified, and parameter fits made for 5ƒ^4 6d7s^2 and 5ƒ^47s^27p.

We present the results of a study of singlet transitions of scandium monochloride, corresponding to (i) the developed redC(2)1Σ+→X1Σ+and infraredB(1)1Π →X1Σ+systems observed in thermal emission, (ii) fluorescence from (3)1Π toB(1)1Π and from (3)1Σ+toB(1)1Π, following excitation by Ar+laser lines 476.5 or 457.9 nm. Transitions belonging to both isotopic molecules45Sc35Cl and45Sc37Cl have been observed, and spectra have been recorded with a Fourier transform spectrometer. We give values of the effective molecular constants for a number of vibrational levels in five electronic states as they result from an overall fit of the experimental data for each isotopomer (some 5400 line wavenumbers are reproduced with a standard deviation of 0.006 cm−1). The (3)1Σ+state is characterized for the first time, in thev= 0 level. Local rotational perturbations are observed in the first five vibrational levels ofB(1)1Π.

Progress has been made in the study of the electronic spectrum of the scandium monochloride molecule. A number of transitions are interpreted, involving five new electronic states,b(1)3Π,A(1)1Δ, (1)1Φ, (2)1Δ, and (3)1Δ, for which molecular constants are determined.

We have measured 6096 Np wavelengths with the 9 m Paschen-Runge spectrograph at Argonne and the Fourier transform facilities at Aime Cotton, of which 40% have been classified as transitions between 130 even levels and 329 odd levels. Most of the even levels and half of the odd levels have been identified by hyperfine structure and Zeeman data. The ground configuration is 5f^46d7s^2; the next configuration, 5f^57s^2, starts at 2831 cm^−1. The low levels of 5f^46d^27s, 5f^36d^27s^2, and 5f^46d7s7p have been identified, and parameter fits made for 5f^46d7s^2 and 5f^47s^27p.

The emission spectrum of ^209Bi has been observed in the infrared region using a Fourier-transform spectrometer at Laboratoire Aimé Cotton, Orsay, using a microwave-excited discharge tube as the light source. In this paper, we report the identification of the 5f–5g, 5f–6g, 5f–7g, and 5f–5g transitions. We have also located the 6d–5f, 6d–6f, 6d–7f, 6d–8f, 6d–9f, 7d–6f, 7d–7f, 7d–8f, and 7d–9f transitions. Using the f–g transitions, we have recalculated the ionization limit of bismuth to be 58 760 ± 1 cm^−1.

This paper is concerned with the study of the 5d states, A' 2Δ, A 2Π and B 2Σ+, (v = 0, 1, 2). It is shown that a complete interpretation of the spectra involving the 5d (v = 0, 1 and 2) states requires a 15 × 15 representation to take account of the spin-uncoupling interaction between A' 2Δ5/2 (v) and A' 2Δ3/2 (v + 1). In the final analysis, the wavenumbers of the 4417 observed lines are fitted simultaneously and reporduced to within a standard deviation of 0·004 cm-1. Deperturbed energies and rotational constants for the v = 0, 1 and 2 levels of the 5d states are obtained. Values of the spin-orbit and rotational interaction constants within this group of 5d levels and of the spin-uncoupling constants BΔ01 and BΔ12 are determined. The implications of the results for the nature of the binding in the 5d states are briefly discussed.

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).

Excited electronic states of RbCs have been rotationally analysed for the first time. Three states in the region 20 000-22 000 cm-1 above the ground state have been characterized by model fitting of upper rotational levels pumped by various Ar+ and Kr+ laser lines. Moreover, IR cross fluorescence between 5000 and 10000 cm-1 has been recorded, allowing for an analysis of two excited states situated between 13 000 and 15000 cm-1 above the ground state. Dissociation products and energies are discussed.

New high-resolution LIF measurements on RbCs, using various Kr+ laser lines have been performed. Transitions to very high vibrational levels of the ground state were observed when using the 568·2nm line. These new data, together with already existing Ar+ LIF data, have made possible a detailed description of the ground state up to near dissociation. An accurate value of the ground state dissociation energy, De=3845±1 cm-1, has been obtained.

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.

Laser-induced fluorescence was observed in the BaCl molecule after excitation by all the Ar+and Kr+ion laser radiations. Several lines of a monomode titanium:sapphire laser have also been used to excite the near-infrared fluorescence. The spectra were recorded by high resolution Fourier transform spectroscopy. The following electronic transitions were rotationally analyzed:A2Π →X2Σ+,B2Σ+→ X2Σ+,C2Π →X2Σ+,C2Π →A′2Δ,C2Π →A2Π,C2Π →B2Σ+,E2Σ+→ C2Π,F2Σ+→ C2Π,F2Σ+→ A2Π,F2Σ+→ B2Σ+. A complete fit was performed, including simultaneously all the measured wavenumbers for these transitions. The observed lines were reproduced with a r.m.s. of 3.9 × 10−3cm−1. In a second analysis theA′2Δ,A2Π, andB2Σ+electronic states were considered as forming ad-complex within each vibrational level. Derived spin–orbit and interaction parameters led to information about the character of the electronic states involved.

The spectrum of neutral ^121Sb emitted by an electrodeless discharge lamp has been observed in the range 2 536–24 786 cm^−1. The wavelengths of 617 lines have been measured. The hyperfine-structure splitting factors of the levels were established for 77% of these lines. Thirty-two new energy levels were found, and several J values were revised. The Slater–Condon method was used for the interpretation of levels in both parities, and the multiconfiguration eigenfunctions were applied to the parametric study of the hyperfine-structure factors A and B. The multichannel quantum-defect theory analysis of high odd levels having J = ½ and J = 3/2 was also revised.