Spectroscopy double resonance

Before commencing our description of true double resonance studies of molecular systems, we describe an extremely important precursor study of the CN radical, which pointed the way to many later experiments. 

Radiofrequency and microwave studies of CN in its excited electronic states 

The CN radical can be produced by the reaction of nitrogen atoms with almost any organic compound, a process which has been extensively studied by electronic emission specttoscopy. The electronic sttucture of CN in its ground state and two relevant excited states may be written in the following simple molecular orbital form. 

The chemical reaction produces CN in excited vibrational levels of the A state, and energy transfer from the v =10 level of the A state to the 0 = 0 level of the B state leads to strong fluorescent emission from the B state. The possibility of detecting microwave transitions in these excited states was investigated by Radford and Broida [3] and first realised experimentally by Evenson, Drum and Broida [4], We will discuss the nature 

Finally, transitions of type (iii) in figure 11.4 were studied by Evenson [6] and by Pratt and Broida [7], These are hyperfine components of an electric-dipole, A-doublet transition within the 2 n3/2 state. They are therefore conventional, except for the enhanced splitting between the /t-doublet states caused by the perturbation from the close-lying 2X state. They are still detected through changes in fluorescent emission from the B 2S+ state. 

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B1.15.5.1 ELECTRON-NUCLEAR DOUBLE RESONANCE SPECTROSCOPY (ENDOR)... 

Tautomers and electronic states of jet-cooled 2-aminopurine investigated by double resonance spectroscopy and theory. Phys Chem Chem Phys 7 3021-3026... 

Kevan, L. and L. D. Kispert (1976). Electron Spin Double Resonance Spectroscopy. New York John Wiley and Sons. 

G.R. Eaton and S.S. Eaton, Electron-nuclear double resonance spectroscopy and electron spin echo envelope modulation spectroscopy, Comprehensive Coordination Chemistry II, Elsevier, Boston, 2004, 49. 

Double-resonance spectroscopy involves the use of two different sources of radiation. In the context of EPR, these usually are a microwave and a radiowave or (less common) a microwave and another microwave. The two combinations were originally called ENDOR (electron nuclear double resonance) and ELDOR (electron electron double resonance), but the development of many variations on this theme has led to a wide spectrum of derived techniques and associated acronyms, such as ESEEM (electron spin echo envelope modulation), which is a pulsed variant of ENDOR, or DEER (double electron electron spin resonance), which is a pulsed variant of ELDOR. The basic principle involves the saturation (partially or wholly) of an EPR absorption and the subsequent transfer of spin energy to a different absorption by means of the second radiation, leading to the detection of the difference signal. The requirement of saturability implies operation at close to liquid helium, or even lower, temperatures, which, combined with long experimentation times, produces a... 

The experimental methods in ENDOR spectroscopy have been extensively described by Kevan and Kispert4) in their monograph, Electron spin double resonance spectroscopy, and by Leniart18 in a recent paper. In this section we shall briefly review the instrumentation used in solid state ENDOR and describe the technical details of some new experimental methods. 

K. Le Barbu Debus, N. Seurre, F. Lahmani, and A. Zehnacker Rentien, Formation of hydrogen bonded bridges in jet cooled complexes of a chiral chromophore as studied by IR/UV double resonance spectroscopy. 2 Naphthyl 1 ethanol/(methanol)n j 2 complexes. Phys. Chem. Chem. Phys. 4, 4866 4876 (2002). 

N. Guchhait, T. Ebata, and N. Mikami, Discrimination of rotamers of aryl alcohol homologues by infrared ultraviolet double resonance spectroscopy in a supersonic jet. J. Am. Chem. Soc. 121, 5705 5711 (1999). 

D. Spangenberg, P. Imhof, W. Roth, C. Janzen, and K. Kleinermanns, Phenol (ethanol) isomers studied by double resonance spectroscopy and ab initio calculations. J. Phys. Chem. A 103, 5918 5924 (1999). 

Kurreck, H., Kirste, B. and Lubitz, W. (1988) Electron Nuclear Double Resonance Spectroscopy of Radicals in Solution - Application to Organic and Biological Chemistry. Weinheim, Germany VCH. 

Electronic absorption spectroscopy charge transfer transitions, 19 71 d-d transitions, 19 70, 71 flavocytochrome b, 36 269-271 intraligand transitions, 19 71-80 of organometallics, 19 69-80 Electronic coupling, between donor and acceptor wave functions, 41 278 Electronic nuclear double resonance spectroscopy, molybdenum center probes, 40 13... 

K. Yamanouchi Recently, we investigated the interatomic potential VRyd(/ ) of the Rydberg states of a HgNe van der Waals dimer by optical-optical double-resonance spectroscopy. It was demonstrated that VRyd(/ ) sensitively varies as a function of the principal quantum number n [J. Chem. Phys., 98, 2675 (1993) ibid., 101, 7290 (1995) ibid., 102, 1129 (1995)], and in the lowest Rydberg states of Hg(7 3S )Ne and Hg(7 5o)Ne, the interatomic potentials exhibit a distinct barrier at around R 4 A. The existence of the barrier was interpreted in terms of a repulsive interaction caused by the Is Rydberg... 

Thus the response of a spatially uniform system in thermodynamic equilibrium is always characterized by translationally invariant and temporaly stationary after-effect functions. This article is restricted to a discussion of systems which prior to an application of an external perturbation are uniform and in equilibrium. The condition expressed by Eq. (7) must be satisfied. Caution must be exercised in applying linear response theory to problems in double resonance spectroscopy where non-equilibrium initial states are prepared. Having dispensed with this caveat, we adopt Eq. (7) in the remainder of this review article. 

Denysenkov, V. P., Prisner, T. F., Stubbe, J., and Bennati, M. (2006). High-field pulsed electron-electron double resonance spectroscopy to determine the orientation of the tyrosyl radicals in ribonucleotide reductase. Proc. Natl. Acad. Sci. USA 103, 13386-13390. 

Pan CF, Hehre WJ, Heat of formation of hydrogen isocyanide by ion cyclotron double resonance spectroscopy, J Phys Chem, 86, 321 (1982)... 

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