B1Π State Research Articles

The potential energy curves of the X 1Σ+ and A 1Σ+ states of LiH

As an important intermediate step in a long-term project to fully understand the spectroscopy of the three lowest singlet states of LiH, (X 1Σ+, A 1Σ+, and B 1Π), we have constructed accurate hybrid potential energy curves for the X1Σ+ and A1Σ+ states to complement earlier work on the B1Π state. In each case the known Rydberg–Klein–Rees (RKR) for low vibrational levels was joined to the long-range region of the potential (represented by new C6, C8, and C10 coefficients reported herein) fixed by the accurately known dissociation limits. The joining was obtained by scaling slightly the ab initio results of Docken and Hinze in the region of interpolation. Extrapolation to smaller distance was also done using ab initio results.

STRUCTURE OF THE BAND SPECTRUM OF CuCl MOLECULE: III. ROTATIONAL STRUCTURE OF THE B AND C SYSTEMS OF Cu65Cl35

The B and C band systems of Cu65Cl35 lying in the region 4600–5200 Å have been photographed in emission under high resolution. Rotational analysis of the (1,0), (0,0), and (0,1) bands of each system has been made. The analysis shows that the B and C systems involve transitions 1Π(B1Π)–X1Σ and 1Σ (C1Σ)–X1Σ respectively. Due to the influence of the closeby C1Σ state, the B1Π state shows appreciable Λ-type doubling. It is found that the B1Π and C1Σ states provide an instance closely resembling the case of Van Vleck's "pure precession". The principal molecular constants obtained for the initial states of the B and C systems of Cu65Cl35 are as follows (cm−1 units):[Formula: see text]

ULTRAVIOLET SPECTRA OF LiH AND LiD

The absorption spectra of LiH and LiD have been observed in the near ultraviolet with high dispersion and absorbing path lengths up to 16 meters. A new band system has been found in each molecule involving the ground state and a 1Π excited state. Rotational and vibrational analyses of this system have been carried out and rotational and vibrational constants for the upper state have been determined. The observed breaking off of the rotational structure of the bands of this B1Π—X1Σ+ system has been interpreted as due to predissociation by rotation. With this assumption very accurate dissociation limits of the B1Π state have been obtained. From these dissociation limits the dissociation energies of the three known electronic states of LiH and LiD have been calculated. In particular the dissociation energies (D0) of the ground states of LiH and LiD have been found to be 2.4288 ± 0.0002 ev. and 2.4509 ± 0.0010 ev., respectively.