Ionization dissociation energies

S = Heat of sublimation of sodium D = Dissociation energy of chlorine / = Ionization energy of sodium = Electron affinity of chlorine Uq = Lattice energy of sodium chloride AHf = Heat of formation of sodium chloride. 

These data can be combined with ionization potential (IP) data according to the scheme below to determine bond dissociation energies (BDE). 

AH and AS to various notional subprocesses such as bond dissociation energies, ionization energies, electron affinities, heats and entropies of hydration, etc., which themselves have empirically observed values that are difficult to compute ab initio. 

Distances Ce are in A, dissociation energies in eV (calculated values are not corrected for the 2ero-point vibrational energy, harmonic frequencies Oe in cm , and adiabatic ionization potentials AEip and electron affinities AEea in eV. Experimental values are from Refs. [94, 159-162]. 

A second role for mass spectrometry in the investigation of reactive intermediates involves the nse of spectroscopy. Althongh an important nse of ion spectroscopy is the determination of thermochemical properties, including ionization energies (addition or removal of an electron), as in photoelectron or photodetachment spectroscopy, and bond dissociation energies in ions, as in photodissociation methods, additional spectroscopic data can also often be obtained, inclnding structural parameters such as frequencies and geometries. 

S.3.4.3. Photodissociation It is also possible to use light as the activation method. Laser sources are especially useful because of their high intensity and narrow wavelength bandwidth. Photodissociation can be used to determine bond dissociation energies in ions directly, similar to what is done with threshold CID, or, alternatively, can be used in conjunction with direct ionization. 

In these experiments, the initial ionization occurs rapidly, and the dissociation energy of AB is determined from the kinetics for its decomposition, which can be measured in a time-resolved experiment, typically within an ion trap. 

Ion extraction. The aspirated or laser ablated sample is transported from the sample introduction system into the center of the torch by a 1 1/min flow of Ar carrier gas where it is immediately dissociated and ionized by energy transfer with the hot -6000 K temperature of the surrounding Ar plasma. Ionization efficiencies are >95% for U and Th (Jarvis et al., 1992). For laser ablation sampling, helium may be employed as the carrier... 

Summary Ab initio calculated bond dissociation energies of silicon compounds will be discussed by means of atomic ionization energies and atomic orbital overlap. Ring strain energies of C- as well as Si-rings are estimated by homodesmotic reactions. The hybridization concept is critically examined in the case of silicon compounds. From the most important results a set of basic rules will be presented. 

Fate of Deposited Energy Ionization, Dissociation, Transfer, and Luminescence... 

As we have seen, several atomic properties are important when considering the energies associated with crystal formation. Ionization potentials and heats of sublimation for the metals, electron affinities, and dissociation energies for the nonmetals, and heats of formation of alkali halides are shown in Tables 7.1 and 7.2. 

An alternative approach to acidities is via a thermodynamic cycle using the bond dissociation energy (DH°), electron affinity (EA) and ionization potential (IP) as follows ... 

Element E Ionization energy E2 bond dissociation energy Spin-orbit 3P2 3Po... 

First ionization energy Second ionization energy Dissociation energy Electron Affinity ... 

The electrochemical behaviour of the compounds containing bonds between silicon and other group-14-metals is also interesting. Mochida et al. reported the electrochemical oxidation potentials of group-14-dimetals [66], As shown in Table 8, there is a good correlation between the oxidation potentials and the ionization potentials which decrease in the order Si-Si > Si-Ge > Ge-Ge > Si-Sn > Ge-Sn > Sn-Sn in accord with the metal-metal ionic bond dissociation energy. 

The reaction of pyridine (py) with bare metal ions (except Fe+) has not been studied widely. The reaction of Fe+ produced by electron ionization of Fe(CO)5 with a mixture of two pyridines (108) was used to compare the proton affinities with the Fe+ affinity. A good correlation was observed. The absolute Fe+ affinity of py was determined to be 49 3 kcal mol-1, which is higher than the value of 44 3 kcal mol 1 for the Fe+-NH3 bond dissociation energy (46). Steric problems with ortho substituted pyridines gave lower than expected affinities. The reaction of py and substituted pyridines showed a maximum addition of four pyridines, similar to the GIB experiments with ammonia (46). 

Table 22. Proton affinity and ionization potential of some transition metal compounds (ML ) and dissociation energy of the cation 2)[(L M-H)+]. All values in kJ mol-1...

Gurvich, L. V., Karachievtziev, G. V., Kondratiev, V. N., Lebedev, Yu. A., Medvedev, V. A., Potapov, V. K., Hodiev, Yu. S. Dissociation energies of chemical bonds. Ionization potentials and electron affinities. Moscow Nauka 1974... 

A large number of tests showed that a value of 0.25 for s was optimal. The mean error in the dissociation energies for 49 diatomic molecules was reduced from 0.2 eV to 0.1 eV. Using an average s was particularly impressive for triply bonded molecules The average error for N2, P2, and As2 was reduced from 0.45 eV to less than 0.15 eV. Similar absolute improvements were obtained for excitation and ionization energies.20... 

Here, and in the following thermochemical schemes, AHs denotes solvation energy, D homolytic bond dissociation energy, I ionization potential, A electron affinity. 

The types of values reported in the database standard enthalpies of formation at 298.15 K and 0 K, bond dissociation energies or enthalpies (D) at any temperature, standard enthalpy of phase transition—fusion, vaporization, or sublimation—at 298.15 K, standard entropy at 298.15 K, standard heat capacity at 298.15 K, standard enthalpy differences between T and 298.15 K, proton affinity, ionization energy, appearance energy, and electron affinity. The absence of a check mark indicates that the data are not provided. However, that does not necessarily mean that they cannot be calculated from other quantities tabulated in the database. 

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