R F Barrow

The Laser Induced Fluorescence Spectrum of Te2 Studied by Fourier Transform Spectrometry

Laser induced fluorescence spectra of separated isotope tellurium dimers, 130Te2 and 128Te2, have been recorded with high precision Fourier transform spectrometry. Fixed frequency argon ion and krypton ion exciting lines ranging from 5145 A to 4067 A have been used and 64 series in 130Te2 and 32 in 128Te2 have been assigned and analyzed. Transitions involving four upper states, A0u+, B0u+ and two states of 1u character, and three lower states, X0g+, X1g and b1Σg+, have been identified. The high sensitivity and excellent frequency calibration of Fourier transform spectrometry have been used to get information about high vibrational levels in the lower states and thence to derive, by simultaneous least squares fits to about 7800 lines in 130Te2 and 1100 lines in 128Te2, estimates of molecular constants valid over wide ranges of v. These have been used to determine RKR potentials and dissociation energies. The very small Ω-doubling constant in X1g has been measured and is shown to have the value expected for interaction solely with X0g+. The character of the states is discussed. There are many perturbations, and intensity distributions show that some transitions are hybrids with parallel and perpendicular components. A0u+ appears to derive from 3Πu and B0u+ from 3Σu-, while the lowest 1u state may be assigned to 3Π1,u. There is fragmentary evidence for a second 1u state in the same region. Among the low lying states of Te2, a1Δg remains to be observed.

Laser-induced fluorescence and two-photon ionisation spectroscopy of the C(3)1Σ+ state of the NaK molecule

The C(3)1 Sigma + state of NaK has been studied by two complementary techniques: laser-induced fluorescence, recorded at high resolution by Fourier transform spectrometry; and two-photon resonant ionisation spectroscopy. Constants for the state, which dissociates to Na(3p 2P12/)+K(4s 2S12/), are Te=17787.3 cm-1, omega e=69.66 cm-1 and re=4.445 AA. These values are compared with the results of recent ab initio calculations.

Rotational analysis of the γ bands of SiF

The rotational analysis of the 0-0, 1-1, 0-1 and 1-2 bands of the γ system of SiF has been completed. The upper state C is most probably 2Δ (case b). Derived constants for this state, in units of cm-1, are as follows: T00 = 39 537.45 (relative to × 2II1/2) ΔG1/2 = 878.38 B0 = 0.600 68 α = 0.005 39 A0 = 2.46.

Rotational analysis of the B-X2, B-X1 and A-X1 systems of gaseous PbF

The B-X2 ( nu 0 27421 cm-1) system of PbF has been photographed in absorption at 2100K in a King furnace, and improved plates of the A-X1 ( nu 0 22502 cm-1) and B-X1 ( nu 0 35697 cm-1) systems have been obtained. Rotational constants are given for the B, A and X states. The large Omega doubling in the A and X1 states is compared to that in the A and X1 states of GeF and SnF, and it is concluded that the A state of PbF is analogous to the A2 Sigma + states of SiF, GeF and SnF. Intensity considerations suggest however that in PbF the state is very nearly a pure case (c) 1/2 state for which Lambda is not well defined.

The identification of a new band system associated with gaseous silicon monoxide

Emission bands tentatively attributed to a new 1 Sigma --1 Sigma - transition of neutral SiO (Bredohl et al. see abstr. A9510 of 1974) are shown to arise from the known E 1 Sigma +-x1 Sigma + system of SiO.

Absorption spectrum of gaseous holmium monofluoride

Bands assigned to two systems of the HoF molecule have been observed in absorption in the region 4500 to 5650 AA. Analysis shows that they have a common lower state which is probably a component of a multiplet ground state with Lambda >2.

Rotational analysis of the C 3Σu--X 3Σg- system of 32S2

The rotational analysis of three bands of the C-X system of 32S2 has been completed. The structure of the bands is similar to that of some of the bands of the main system B 3Σu--X 3Σg- in which, in addition to the six main branches, the branches NP13, PR13, RP31 and TR31 also appear with appreciable strength. Constants (cm-1) for state C are as follows: Te = 55 58166 ωe = 82915 ± 032 xeωe = 334 ± 010 Bo = 0321 15 ± 0000 10 107Do = 22 ± 02, λo = -1161 ± 021 γo = +0033 ± 0001 re = 1810 Angstrom It appears that C is a Rydberg state, with the likely configuration... σg2πu4πg(πu4p).

A medium-resolution study of fluorescence in 80Se2 excited by lines of the argon-ion laser

Some twenty series excited in gaseous 80Se2 by lines of the Ar+ laser have been photographed at moderate resolution. They arise from transitions B0u+-X0g+ B1u-X1g and from cross transitions B1u-XOg+ and B0u+-X1g. Measurements in the range 6< nu <12 and 58<J<202 lead to Delta nu 10(X1g-0g+)=509.5+2.1256( nu +1/2) cm-1 and Delta nu 10(B1u-B0u+) becomes 75.45 cm-1. Some consequences of the new values are briefly discussed.

Electronic states of Bi2

Laser-induced fluorescence and thermal emission spectra of Bi2 have been recorded at high resolution by Fourier transform spectrometry. Extensive analyses, involving the assignment of more than 20 000 lines, have been made of transitions involving the states X 0+ g, a lu(3Σ+ u), A 0+ u(3Σ- u) and E lg. The electronic states of Bi2 are reviewed, and comparison is made with the results of ab initio calculations.

Fluorescence and absorption spectra of gaseous TeSe

Fluorescence spectra of gaseous, isotopically pure samples of TeSe, excited by five lines of the argon ion laser have been measured and the D-X systems of 128Te 78Se have been photographed in absorption at moderate resolution. Combination of the results has led to an analysis of the twenty-one observed fluorescence series into transitions between four upper states (or sub-states) and two lower states, x 0+ and x 1. Constants (cm-1) for the ground state of 128Te 78Se are derived.