C. Effantin

Long-range potentials for the X1∑g+ And (1)1Σg states and the dissociation energy of Na2

Fluorescence excited in the A 1 ∑ u + -X 1 Σ g + system of Na 2 by a ring dye laser gives information about levels up to υ=62 in X 1 Π g + some 5 cm −1 from the dissociation limit. Ultraviolet lines of Kr III (and Ar III) lasers excite C 1 Σ u , (2) 1 Π u + -(1) 1 Σ g fluorescence in the infrared which allows the positions of levels in (1) 1 Σ g to within ≈ 55 cm −1 of the dissociation limit to be derived. The dissociation energy D e is estimated to be 6022.6 ∓ 1.0 cm −1 . The levels of both states are in satisfactory agreement with theoretical predictions.

Long-range potentials for the X 1Σ+ and a 3Σ+ states of the NaK molecule

Fluorescence spectra of the NaK molecule excited by the 4765 A and 4880 A lines of an argon-ion laser have been recorded at high resolution by Fourier-transform spectrometry. Constants for the ground state X 1Σ+ and for the first excited state, a 3Σ+, have been determined from a simultaneous least-squares fit to a total of 1758 lines assigned to five systems. Rotationless potentials for these two states have been calculated at internuclear distances out to about 9·3 A for the ground state and to about 9·1 A for the triplet state. The dissociation energy, D e (NaK), is found to be 5274·9 ± 0·5 cm-1, and the long-range potential for X 1Σ+ is given by with V in cm-1, r in A. Values of the potential constants are in satisfactory agreement with the results of recent calculations.

Interactions between A 1Σu+ and b 3Πu states of Na2

Following excitation to the B(1) 3 Pi u// state of Na2 by the 4880 and 4965 AA lines of an argon-ion laser, the collision-induced system (2) 1 Sigma g+-A(1) 1 Sigma u+ was recorded at high resolution by Fourier-transform spectrometry. The A(1) 1 Sigma u+ approximately b(1) 3 Pi u interactions were studied in detail. The electronic part of the interaction matrix element (3 Pi 0,u mod Hso mod 1 Sigma u+) is independent of nu (b 3 Pi ) for the Li Li et al. (1984) numbering and is found to be 5.91+or-0.14 cm-1.

Laser-induced fluorescence of NaK: the b(1) 3Π state

Laser-induced fluorescence of the NaK molecule has been recorded at high resolution by Fourier-transform spectrometry in the region 4000-9500 cm-1. Fourteen series excited by the Ar+ 4765, 4880 and 5287 AA lines have been assigned to the system D1 Pi , d3 Pi to b3 Pi . The strongest transitions, at low values of J, are Omega =1 to Omega =1, but there are also series that arise from Omega =2 to Omega =2 and from Omega =0 to Omega =0. The lower state, the second excited triplet state of NaK, has not been observed before. Constants (in cm-1) for b3 Pi 1 are as follows: Te=11562.18, omega e=120.41, omega exe=0.3425, Be=0.095066 and alpha e=3.28*10-4. The spin-orbit coupling constant A is estimated to be 15.577 cm-1 and the internuclear distance re is 3.502 AA. The results are in good agreement with pseudopotential and ab initio calculations.

High-resolution Fourier spectrometry of the CO infrared emission spectrum: Perturbation analysis of the a′ 3Σ-a3Π system

Abstract The strongly perturbed a′ 3 Σ -a 3 Π system of CO was recorded under high resolution with a Fourier transform interferometer. Rotational perturbations observed in the a′ 3 Σ v = 0, 1, 3 levels, due to an interaction with high levels of the a state, were completely reduced. The treatment required a theoretical model which takes into account an off-diagonal spin-spin parameter and the centrifugal distortion of off-diagonal interactions between 3Π and 3Σ states.

Fourier-transform spectrometry of laser-excited fluorescence in Na2

Abstract Fluorescence excited by UV lines of the krypton-ion laser has been recorded by high-resolution Fourier-transform spectrometry in the region 10000-3500 cm −1 . Preliminary values of the constants for three new electronic states. (2) 1 Σ + g , (1) 1 Π g and (3) 1 Σ + g and for several levels of excited 1 Σ + u states are given.

Interactions between the A(1) 1Σ+u and b(1) 3Πu states of K2

Infrared laser-excited fluorescence spectra of the A(1) 1Σ+u - X(1) 1Σ+g system of K2 have been recorded at high resolution by Fourier transform spectrometry. Perturbations in A 1Σ+u are attributed to spin-orbit-induced interactions with levels of the well bound triplet state, b(1) 3Πu, and analysis leads to estimated values of molecular constants for both interacting states.

The ground state of KRb from laser-induced fluorescence

The A1 Sigma +-X1 Sigma + system of KRb was excited using a titanium-doped sapphire laser. Fluorescence spectra were recorded on a Bomem Fourier transform spectrometer, using an apodised linewidth of 0.045 cm-1. Rotational and vibrational constants are reported for the ground state, X1 Sigma +, covering the range 0<or=v<or=44 and J<141.

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).