The electronic emission spectrum of triatomic hydrogen. III. Infrared perpendicular bands near 3600 cm⁻¹

Abstract

The experimental techniques for obtaining spectra of triatomic hydrogen are described with special reference to studies in the infrared. An electronic transition near 3600 cm−1 is observed in both H3 and D3. Its analysis shows that it is a 2A1′–2E′ transition and that the upper state is identical with the upper state 3s2A1′ of the 6025 Å band previously analysed (I. Dabrowski and G. Herzberg. Can. J. Phys. 58, 1238 (1980)) while the lower state is the upper state 3p2E′ of the 7100 Å band (G. Herzberg and J. K. G. Watson. Can. J. Phys. 58, 1250 (1980)). Improved constants are obtained for both these states from the infrared bands of H3 and D3. Perturbations in the upper state 3s2A1′ of D3 are clarified.

The Jahn–Teller effect in the 3 pe ′ Rydberg state of H 3 : review of experimental and ab initio determinations

“…Note incidentally that the same is not true for the quantum defect at the conical intersection: while the frozen-core calculations of Nager & Jungen [8] predicted a value m = 0.346, the determination of Mistrík et al [6] derived from a highly correlated electronic wave function yielded m = 0.406, that is, a significantly increased value corresponding to a lowering of the 3pe pair of states by 700 cm −1 . Similarly, the values for the depth of the JT-induced potential minimum determined by Herzberg et al [12], and more recently by Vervloet & Watson [13], also turn out to be consistent with the various quantum-chemical determinations. Herzberg et al [12] and Vervloet & Watson [13] derived their values from the observed rotational structure of the 3pe manifold of levels combined with the vibrational frequency of the 3pe Rydberg state predicted in the study of King & Morokuma [18].…”

“…Similarly, the values for the depth of the JT-induced potential minimum determined by Herzberg et al [12], and more recently by Vervloet & Watson [13], also turn out to be consistent with the various quantum-chemical determinations. Herzberg et al [12] and Vervloet & Watson [13] derived their values from the observed rotational structure of the 3pe manifold of levels combined with the vibrational frequency of the 3pe Rydberg state predicted in the study of King & Morokuma [18]. The value 86.1 ± 0.7 cm −1 , which we obtain here for the same state, is in quite good agreement with the values given there, viz.…”

“…It is instructive to compare the JT terms for n = 3 from table 2 with those derived from high-resolution emission spectroscopy in the 1980s [11,12], as well as with those derived previously by various authors from quantum-chemical potential surfaces [6,7,8,18]. This requires converting the definitions and coordinates used in previous papers to the ones used here.…”

“…The value 86.1 ± 0.7 cm −1 , which we obtain here for the same state, is in quite good agreement with the values given there, viz. 87.0 cm −1 [12] and 89.1 cm −1 [13]. The value D n u + 2 = 75.9 cm −1 used in our previous paper [10] for evaluating equation (1.1) is seen to be about 15 per cent too small (cf.…”

Internal rotation in Jahn–Teller coupled systems: The ethene and allene cations

“…[1,2,3,4] and references therein). Most treatments focused on the E⊗e JT effect and on the rovibronic energy level structures of prototypical molecular systems including H 3 [5,6], Li 3 [7], Na 3 [8], CH 3 O [9,10], cyclopentadienyl [11,12], C 6 H + 6 [13,14,15] and C 5 H + 5 [16,17]. The vibronic coupling of a doubly-degenerate electronic state mediated by nondegenerate vibrational modes, i. e., the E⊗(b 1 ⊕b 2 ) or E⊗b JT effects apparent in molecules with a four-fold symmetry axis, has received less attention, maybe because it is considered to be the simplest [3].…”