Joel Tellinghuisen

Transition strengths in the visible–infrared absorption spectrum of I2

The contributions of the 1Πu←X, B←X, and A←X transitions to the absorption coefficient of I2 in the 4200–8000 A region are reassessed in light of recent results concerning the 1Πu and A potentials and their diffuse absorption spectra. Earlier estimates of the continuum underlying the B←X discrete spectrum are augmented by additional high‐resolution ’’between‐the‐lines’’ absorption measurements, corrected for residual B–X absorption using the very reliable spectroscopic constants now available for this system. The 1Πu–X and A–X systems are now estimated to be about 10% weaker than in the previous analysis [J. Tellinghuisen J. Chem. Phys. 58, 2821 (1973)]. For the region 2.6–2.8 A sampled in absorption, the estimates of the B–X transition strength ‖μe‖2 remain close to the previous values.

Spectroscopic studies of diatomic noble gas halides. II. Analysis of bound‐free emission from XeBr, XeI, and KrF

The strong ultraviolet emission bands (’’Spectrum I’’) of XeBr, XeI, and KrF have been photographed following electron‐beam excitation of appropriate noble gas/halide mixtures at moderate to high pressures. These diffuse spectra are analyzed through trial‐and‐error theoretical simulations. The upper‐state vibrational frequencies are estimated to be 120±10, 112±8, and 310±20 cm−1 for XeBr, XeI, and KrF, respectively. The analysis also yields approximate shapes for the lower‐state potential curves in the Franck–Condon region. Lasing is observed in XeBr (2818 A) and KrF (2484, 2491 A) but not in XeI.

The dispersed fluorescence spectrum of NaAr: Ground and excited state potential curves

The van der Waals molecule NaAr has been prepared by supersonic free jet expansion of a mixture of sodium, argon, and helium. The A 2Π←X 2Σ+ electronic transition has been excited by a tunable dye laser and the resulting A→X fluorescence has been studied. The dispersed fluorescence spectra display both discrete and diffuse features, corresponding to transitions from excited vibrational levels of the A state to bound and unbound levels of the X state. The characteristic reflection structure in the bound‐free spectra permits an unambiguous assignment of the vibrational numbering in the A state. This assignment and the previously measured spectroscopic constants are used to calculate the potential curve of the A state. The discrete structure in the fluorescence spectra is analyzed and, together with the previous measurements, is used to determine the potential curve of the X state in the well region. The repulsive part of the X curve is then deduced through trial‐and‐error simulation of the biund‐free spectr...

Spectroscopic studies of diatomic noble gas halides: Analysis of spontaneous and stimulated emission from XeCl

A XeCl emission band system with peak intensity near 3080 A is reported and analyzed. The vibrational analysis of this spectrum includes 24 violet‐degraded bands assigned to Xe35Cl and Xe37Cl, and yields (for Xe35Cl) ΔTe=32 405 cm−1, ωe′=195.2 cm−1, ωe″=26.3 cm−1, and De″=255 cm−1. The weakly bound 2Σ+ ground state of XeCl resembles a van der Waals state, whereas the excited state is the analog of the CsCl ground state. Approximate potential curves are derived for these XeCl states. Lasing is observed on the 0–1, 0–2, and 0–3 bands of this transition, with a peak output power of 1.5×104 W.

Spectroscopic studies of diatomic noble gas halides. IV. Vibrational and rotational constants for the X, B, and D states of XeF

The B→X and D→X systems of XeF are recorded by photographing the emission from the low‐pressure Xe*/XeF2 and Ar*/XeF2 reactions. A rotational analysis is obtained for the 1–2 band of B–X, for which isotopic blending is negligible. Vibrational parameters for the X, B, and D states are derived from a direct, weighted least‐squares fit of all assignments for both transitions. Rotational parameters are deduced from the vibrational dependence of the band shapes and intensities. Some significant results of this analysis are ReX=2.293 a, ReB=2.631 a, ReD=2.51 A, ωeX=225 cm−1, ωeB=309.0 cm−1, ωeD=350.1 cm−1, and DeX=1175 cm−1. The Franck–Condon factors for many of the bands in both systems show a strong rotational dependence, which is to be expected in transitions of this type, for reasons discussed herein.

The ultraviolet laser transitions in I2 and Br2

Abstract Vibrational analyses are given for the ultraviolet laser transitions in I2 (≈3400 A) and Br2 (≈2900 A). Both systems are attributed to the 1432, 2g3Π → 2431, 2u 3Π transition. This designation contradicts all previously published analyses and represents the first identification of the predicted 2u 3Π valence state in these molecules.

Potentials for weakly bound states in I2 from diffuse spectra and predissociation data

Potential curves are derived for the 2431 1Πu and 2341 a(1g 3Π) states of I2 using existing data from several sources. Compared with previous estimates, the new potentials are thought to be valid over a wider range of internuclear distance, spanning the shallow bound wells at large R (>4A) and the repulsive regions where they cross the well‐known B(O+u 3Π) state at small R (<3.3 A). Seven of the ten Hund’s case (c) molecular states which correlate with ground‐state I atoms are now known experimentally, including three which cross the B state. The role of these states in the collisional quenching of B and in the geminate recombination of I atoms is considered.

Noble gas halides: The B → X and D → X systems of 136Xe35Cl

Abstract The B → X (2870–3100 A) and D → X (2250–2370 A) band systems of 136Xe35Cl are photographed and vibrationally analyzed. A simultaneous least-squares fit of 41 band-heads in the B-X system and 35 in D-X yields, in part, the following constants (in cm−1): TeB = 32 405.8, TeD = 42 347.9, ωeB = 194.75, ωeD = 204.34, ωeX = 26.22. The ground state dissociation energy ( D ″e) is estimated to be 281 ± 10 cm−1. Potential curves are derived for all three states through Franck-Condon calculations. From these curves the D-state internuclear distance is 0.09 ± .02 A smaller than the B-state distance.

Spectroscopic studies of diatomic noble gas halides. III. Analysis of XeF 3500 Å band system

B→X spontaneous and stimulated emission spectra of XeF have been photographed at medium resolution (2.0 A/mm) and vibrationally analyzed. The assignments are made with the aid of trial‐and‐error Franck–Condon calculations and band profile simulations, which are described in detail. The strong laser emission near 3511 A is primarily due to densely overlapped rotational lines in the 1–4 vibronic band, and that near 3532 A probably includes numerous rotational transitions in the 0–2, 0–3, and 1–6 bands.

Analysis of the 2770-Å emission system in I2

Abstract A weak emission spectrum of I2 near 2770 A is reanalyzed and found to to minate on the A(1u3Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward I − ( 1 S) + I + ( 3 P 1 ) . In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″e = 10 907 cm−1, D ″e = 1640 cm−1, ω″e = 95 cm−1, R″ e = 3.06 A ; T′e = 47 559.1 cm−1, ω′e = 106.60 cm−1, R′ e = 3.53 A .