CPCD Differential Equations

CPCD Differential Rate Equations

Definitions

Neutralization reactions

Matrix-analyte charge transfer reactions

Analyte-analyte charge transfer reactions

Matrix pooling ionization

Here is some information on excited state thermal ionization.

The ablation plume

The ablation plume expansion is treated as a molecular beam, see J. Mass Spectrom. v. 37, p. 867 (2002) for more discussion..

x=downstream distance, d=laser spot diameter

Rate of temperature change vs time after expansion start:

Bimolecular reaction rates are modulated by the local diffusion constant and pressure ratio

Secondary ion-molecule reactions

See Anal. Chem. v. 75, p. 2199 (2003) for further discussion of the following parameters.

An Arrhenius-type reaction rate is assumed. As listed above, activation energies and preexponential factors are needed for proton transfer (PT), inverse proton transfer (back-transfer) (IPT) as well as deprotonation (DP) and inverse deprotonation (IDP) charge transfer reactions. If the forward reaction is exoergic:

The hard-sphere prefactor is the collision rate, corrected for the different sizes of matrix and analyte, and the sample composition:

Where V_Mand V_Aare the sound speeds of matrix and analyte, F is the mole fraction of analyte, and n the total number density. The molecular radii, R_i (cm), are given by:

where λ is typically 14-19 kJ/mol.

Rate Equations

Matrix ground electronic state:

Matrix first excited singlet state

Matrix higher excited singlet state:

Matrix positive ions:

Matrix negative ions:

Non-electronic internal energy (QE= quantum efficiency, IP=ionization potential):

Analyte 1 neutrals, positive and negative ions

Analagous equations for analyte 2 neutrals, positive and negative ions.

Note: this page was generated manually, not automatically from the original code. It is not guaranteed to be free from errors or omissions.

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