Excitation energy spectroscopic constants

The theory of resonance transfer of electronic excitation energy between donor and acceptor molecules of suitable spectroscopic properties was first presented by Forster.(7) According to this theory, the rate constant for singlet energy transfer from an excited donor to a chromophore acceptor which may or may not be fluorescent is proportional to r 6, where r is the distance... 

Fig. 2. Flash spectroscopic rate constants for triplet energy transfer from donors of various excitation energies to biacetyl and to m-stilbene.

An extensive compilation of RKR potential curves for NO+ has recently been reported by Albritton, et. al.87 Their studies include all of the experimentally known electronic states of NO+ below 24 eV. Potential energy curves and spectroscopic constants are tabulated and estimates of accuracy in the location of the excited states are reported. 

The resonance Raman spectra of Fe2, NiFe, Vz, T 2 and Ni3 in solid, rare-gas matrices are reviewed. Spectroscopic constants for these were (WgjtOgXg, cm ) Fe2 (300.26, 1.45), NiFe (320.0, 1.32), V2 (508.0, 3.3) and Ti2 (407.9, 1.08). A Bernstein-LeRoy analysis was performed on the data for Fe2, yielding a bond dissociation energy of 1.2 eV, close to that reported by Kant. All of the transition metal diatomlcs studied showed an Inordinate ability to remain vibrationally excited when the first few vibrational levels were populated radiatively. This gave rise to intense antistokes... 

Sodium, energy bands as a function of atomic spacing, 179-180 sp hybrid orbital, features, 144 sp hybrid orbital, features, 144 sp hybrid orbital, features, 144-146 Spectroscopic constants asynunetric rotors, 229 diatomic molecules, 227 electronic excitation, see Electronic excitation... 

Obstacles to modelling the evolution of quantum state populations under multiple collisions primarily arise from the complexity of standard collision theory. An accurate PES is needed for all potential collision partners in a gas mixture and some species will be in highly excited states. State-to-state collision calculations are highly computer intensive for even the simplest of processes and, without a major increase in computational speed, are not suited to multiple, successive calculations. By contrast, the AM method is fast, accurate and calculations for atoms and/or diatomic molecules require only readily available data such as molecular bond length, atomic mass, spectroscopic constants and collision energy. 

Chemiluminescence in the 450- to 360-nm range resulting from collisions of P" ions with H2 or D2 molecules (center-of-mass kinetic energies Ec.m. = 2.3 to 12.2 eV) was Identified with the A- X emission of PH+ and PD+ ions. A spectral analysis has been performed at the maximum cross section (Ecm. = 6.4 eV) by comparison with computer-simulated spectra which were based on the spectroscopic constants of [7, 9, 10] besides the already known 0- 1, 0 0, and 1- 0 bands, some new bands, 1- 1 for PH+ and 2 0, 1- 2, 0 2 for PD+, could be localized. Additional experiments were carried out to verify that the observed emission is indeed due to the chemiluminescent exchange reaction P ( P, D)+H2 PH-"(A 2A)+H and not to collisionally excited PH+ impurities in the P+ beam [11]. 

The first factor is associated with the electronic dipole transition probability between the electronic states the second factor is associated between vibrational levels of the lower state v" and the excited state V, and is commonly known as the Franck-Condon factor, the third factor stems from the rotational levels involved in the transition, J" and /, the rotational line-strength factor (often termed the Honl-London factor). In particular, the Franck-Condon information from the spectrum allows one to gain access to the relative equilibrium positions of the molecular energy potentials. Then, with a full set of the spectroscopic constants that are used to approximate the energy-level structure (see Equations (2.1) and (2.2)) and which can be extracted from the spectra, full potential energy curves can be constructed. 

Das and Balasubramanian (1991c) have computed the spectroscopic constants and potential-energy curves of LaH. They used a C ASSCF method followed by full second-order Cl calculations in conjugation with 5s 5p 5d6s RECPs of Ross et al. (1990). The basis set used was (5s5p3d) valence Gaussian basis set. At both CASSCF and SOCI levels, excitations from the 5s 5p shells were not allowed. The CASSCF calculations... 

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