Vibronic spectroscopy

Myers A B, Tchenio P and Moerner W E 1994 Vibronic spectroscopy of single molecules exploring electronic-vibrational frequency correlations within an inhomogeneous distribution J. Lumin. 58 161-7... 

The entire approach presupposes the separation of electronic degrees of freedom. As already noted, for the higher electronic states of polyatomic molecules, there can be important couplings with both spectroscopic and dynamic implications. The vibronic spectroscopy of benzene is reviewed by Ziegler and Hudson (1982). 

In principle these terms may be directly evaluated by vibronic spectroscopy, since diAcOi is just the "vibrational shift . For example, the frequency of mode 8 is 7 cm higher in pDFB-Ar than in pDFB. Then Eq. (11.8) gives AV o°), 8 ) = 2 x7 cm l = S.Ocm at the equilibrium value of r. Remarkably few assumptions are required to relate AcOi to the rate of vibrational predissociation of a van der Waals molecule with mode i excited.while the exact form of Eq. (I1.8) relies on the harmonic approximation... 

P.Y. Cheng and M.A. Duncan, Vibronic Spectroscopy and Dynamics in the Jet-Cooled Silver Trimer , Chem. Phys. Lett. 152, 341 (1988). 

A change in the electronic state of a molecule is normally accompanied by a change in the vibrational state as well. When we resolve different vibrational transitions within an electronic spectrum, we call this vibronic spectroscopy. Labeling the upper state by primes and lower state by double-primes, the energy difference between the two quantum states of the transition is given by... 

Ro-vibronic spectroscopies in the UV-Visible-Infrared and Micro-wave energy range, X ray and electron diffraction, incoherent and coherent elastic and inelastic neutron scattering, Raman scattering. Nuclear Magnetic resonances etc. all contain a vibrational contribution. Other non spectroscopic properties such as the various thermodynamical quantities contain the vibrational contributions. 

Wang C, Mohney B K, Williams R, Hupp J T and Walker G C 1998 Solvent control of vibronic coupling upon intervalence charge transfer excitation of (NC)gFeCNRu(NH3)g- as revealed by resonance Raman and near-infrared absorption spectroscopies J. Am. Chem. Soc. 120 5848-9... 

Vibrational transitions accompanying an electronic transition are referred to as vibronic transitions. These vibronic transitions, with their accompanying rotational or, strictly, rovibronic transitions, give rise to bands in the spectrum, and the set of bands associated with a single electronic transition is called an electronic band system. This terminology is usually adhered to in high-resolution electronic spectroscopy but, in low-resolution work, particularly in the liquid phase, vibrational structure may not be resolved and the whole band system is often referred to as an electronic band. 

In electronic spectroscopy of polyatomic molecules the system used for labelling vibronic transitions employs N, to indicate a transition in which vibration N is excited with v" quanta in the lower state and v quanta in the upper state. The pure electronic transition is labelled Og. The system is very similar to the rather less often used system for pure vibrational transitions described in Section 6.2.3.1. 

Single vibronic level, or dispersed, fluorescence spectroscopy... 

Techniques other than UV-visible spectroscopy have been used in matrix-isolation studies of Ag see, for example, some early ESR studies by Kasai and McLeod 56). The fluorescence spectra of Ag atoms isolated in noble-gas matrices have been recorded (76,147), and found to show large Stokes shifts when optically excited via a Si j — atomic transition which is threefold split in the matrix by spin-orbit and vibronic interactions. The large Stokes shifts may be explained in terms of an excited state silver atom-matrix cage complex in this... 

It is relatively easy to decide which vibronic bands have a common origin. This is accomplished by observing the phosphorescence intensity change of each band upon microwave saturation at a frequency that corresponds to transitions between rz and tx. This is known as phosphorescence-microwave double resonance (PMDR) spectroscopy. These frequencies for 2,3-dichloroquinoxaline are given in Table 6.3. 

A final study that must be mentioned is a study by Hartmann et al. [249] on the ultrafast spectroscopy of the Na3F2 cluster. They derived an expression for the calculation of a pump-probe signal using a Wigner-type density matrix approach, which requires a time-dependent ensemble to be calculated after the initial excitation. This ensemble was obtained using fewest switches surface hopping, with trajectories initially sampled from the thermalized vibronic Wigner function vertically excited onto the upper surface. 

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