Energy-Resolved Measurements

Cavanagh R R, Fleilweil E J and Stephenson J C 1994 Time-resolved measurements of energy-transfer at surfaces Surf. Sc/. 300 643-55... 

Energy-resolved CID can be used to measure bond dissociation energies directly, and therefore is readily applicable for the determination of ion affinities. However, Graul and Squires have also described a method for measuring gas-phase acidities using CID of carboxylates. ° Upon CID, carboxylate ions, RCO2, undergo decarboxylation to form the alkyl anions, R, ... 

Threshold CID can be used to measure the energy required for decarboxylation, in order to determine the enthalpy of formation of R, which can be used to calculate the gas-phase acidity. While nominally straight-forward, the decarboxylation approach is limited to systems that have a bound anion, R, and requires an instrument with the capability of carrying out energy-resolved CID. However, it does have an advantage of being a regiospecific approach. 

The combination of state-of-the-art first-principles calculations of the electronic structure with the Tersoff-Hamann method [38] to simulate STM images provides a successful approach to interpret the STM images from oxide surfaces at the atomic scale. Typically, the local energy-resolved density of states (DOS) is evaluated and isosurfaces of constant charge density are determined. The comparison between simulated and measured high-resolution STM images at different tunneling... 

Wu P. and Brand L. (1992) Orientation Factor in Steady-State and Time-Resolved Resonance Energy Transfer Measurements, Biochemistry 31, 7939-7947. 

The least resolved measurement is determination of the isothermal rate constant k(T), where T is the isothermal temperature. Although conceptually simple, such measurements are often exceedingly difficult to perform for activated process without experimental artifact (contamination) because they require high pressures to achieve isothermal conditions. For dissociative adsorption, k(T) = kcol (T) [S (Tg = TS = T)), where kcol(T) is simply the collision rate with the surface and is readily obtainable from kinetic theory and Tg and T, are the gas and surface temperatures, respectively [107]. (S ) refers to thermal averaging. A simple Arrhenius treatment gives the effective activation energy Ea for the kinetic rate as... 

Energy-resolved rate constant measurements near the threshold for diplet methylene formation from ketene have been used to provide confirmation of the fundamental hypothesis of statistical transition state theory (that rates are controlled by the number of energetically accessible vibrational states at the transition state).6 The electronic structure and aromaticity of planar singlet n2-carbenes has been studied by re-election coupling perturbation theory.7 The heats of formation of three ground-state triplet carbenes have been determined by collision-induced dissociation threshold analysis.8 The heats of formation of methylene, vinylcarbene (H2C=CHCH), and phenylcarbene were found to be 92.2 3.7, 93.3 3.4, and 102.8 33.5 kcal mol-1, respectively. 

Activation Energies BA for DMABN in Different Polar Solvents, as Determined from Integrated Time-Resolved Measurements,88 and Comparison to Ev, the Activation Energy... 

Figure 9. Detector for performing energy and angle-resolved measurement of neutrals desorbed from surfaces.

This obviously has a physical reason. Since condensed systems are investigated, interaction with the environment is involved in the transition. The chromophore is an open system which dissipates vibrational energy into the surrounding medium by irreversible processes. This phenomenon can be used for detecting fine structure from the time resolved measurements of photon events, by monitoring the correlations between successively emitted photons. This new technique will be reported in the second part of this article. 

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