Chen The electron capture detector

REFERENCES 327

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APPENDICES

Appendix I is a glossary of terms, acronyms, and symbols.

Appendix II presents the structures of organic compounds. Structure 1 provides the number, names, and adiabatic electron affinities of the Bergman Dewar set. Structure 2 gives the adiabatic electron affinities, gas phase acidities, and names of the DNA and RNA bases. Structure 3 shows the charge transfer complex acceptors. Structure 4 gives the numbering system of naphthalene and biphenyl and compares the structures of acenaphthylene and biphenylene.

Appendix III examines the general least-squares procedure. The normal leastsquares solution is compared to the general least-squares solution that allows multiple variables, variable weights in all data, and the use of data determined from other experiments to be combined with that from a specific experiment. The data reduction for a linear plot of ln(KT3=2) versus 1,000/T for acetophenone as a function of reaction time is illustrated. The intercept can be improved by using the weighted average value of the Ea of acetophenone. This is an example of combining data and their uncertainties in the general least-squares solution.

The tables in Appendix IV summarize the evaluated values of the electron affinities given in this book. The electron affinities of the atoms and homonuclear diatomic molecules are given in two tables, A1.1 and A1.2. The references for both tables are combined. The electron affinities of the hydrocarbons are given in Tables A2.1 and A2.2. Tables A2.3 and A2.4 provide the electron affinities of the halogenated hydrocarbons. The odd-numbered tables are ordered by value and the even-numbered tables are ordered by molecular weight. The references for the hydrocarbons are given separately from those of the CHX compounds. Tables A3.1 and A3.2 list the values for the CHNX molecules. These were combined because there are so few halogenated compounds. Tables A4.1 and A4.2 contain the electron affinities of the CHO and CHOX compounds, while Tables A5.1 and A5.2 contain those of the CHON and CHONX compounds.

Searching the NIST tables by combination of elements, for example, CHO, generated Tables A2 through A5. The list contains both radicals and molecules.

The Electron Capture Detector and the Study of Reactions with Thermal Electrons by E. C. M. Chen and E. S. D. Chen

ISBN 0-471-32622-4 # 2004 John Wiley & Sons, Inc.

329

330 APPENDICES

Approximately 170 entries were returned. These were saved in a text file. Less than half of these are for molecules. After eliminating the radicals, the text file was loaded into a spreadsheet, the molecular weights calculated, and the electron affinities in the NIST tables evaluated by taking the weighted average of the values for the same state of a molecule. Values not listed in the NIST table were also included in the weighted average. The revised ECD values were used to adjust the TCT values scaled to the ECD values for benzaldehyde, acetophenone, and benzophenone. For example, the weighted average of the ECD Ea for benzaldehyde is 0.457(5), about 0.03 eV higher than the NIST value. The TCT values scaled to the NIST value have been revised upward by this amount.

In Table A6.1 the names and electron affinities of the Bergman Dewar hydrocarbon set are given. The structures for these compounds are shown in Appendix III along with the electron affinities and Bergman Dewar number. The gas phase electron affinities that are significantly different from the NIST values are tabulated in Table A6.2. This is simply a compilation of the values in the earlier appendices. Table A6.3 lists the gas phase values determined primarily by ECD that are not listed in the NIST tables. Included are some values that could apply to excited states. The excited-state values for cytosine, thymine, and uracil obtained by interpreting hydrated PES spectra are given. Table A6.4 presents the data for hydrated purines. Table A6.5 contains the electron affinities of charge transfer complex acceptors not in the NIST tables. Tables A6.6 and A6.7 list the electron affinities obtained from half-wave reduction potentials also not contained in the NIST tables.

APPENDIX I

Glossary of Terms, Acronyms,

and Symbols

Accuracy	The agreement between the measured quantity and the ‘‘true’’
	value. The difference is due to systematic uncertainties, as opposed
	to random uncertainties that define precision.
Ai	Pre-exponential term for rate constants. Subscript 1 stands for
	attachment, 1 detachment, 2 dissociation, D recombination of
	electrons, N recombination of anions, ET electron transfer of ions,
	ET reverse of electron transfer.
AB	General molecule.
AB( )	Anion of AB.
AEa	Adiabatic electron affinity, energy difference between the ground
	state of the anion and the most stable state of the neutral molecule.
AM1	A particular semi-empirical self-consistent field calculation. It
	stands for Austin Model-1.
AMB	Alkali metal beam formation of ion pairs.

bExponential constant in the Morse potential function. With m as the reduced mass b ¼ neð2p2m=De½X2&Þ1=2.

C1	Constant relating the energy for a charge transfer absorption
	maximum to the electron affinity of the acceptor and the ionization
	potential of the donor. See equation 2.23.
C2	Second constant relating the energy for a charge transfer absorption
	maximum to the electron affinity of the acceptor and the ionization
	potential of the donor. See equation 2.23.
CEC	Abbreviation for CURES-EC in the tables.
CURES-EC	The use of semi-empirical multiconfiguration configuration
	interaction quantum mechanical procedures to estimate electron

331

332	APPENDIX I
		correlation in the calculation of electron affinities, gas
		phase acidities, ionization potentials, and bond dissociation
		energies.
DEC (1 or 2)		Compounds under dissociative electron capture in the ECD.
		DEC(1) refers to molecules that can dissociate unimolecularly
		via a single potential energy curve. DEC(2) refers to molecules
		that can dissociate via a negative-ion intermediate.
DðmÞ		Designation of HIMPEC with m ¼ 0 to 3. This indicates dissocia-
		tion in the Franck Condon region and the number of values of Ea,
		VEa, and EDEA that are positive. This stands in contrast with
		MðmÞ.
DcðmÞ		Designation of HIMPEC with m ¼ 0 to 3. This indicates dissocia-
		tion in crossing the long-range curve and the number of values of
		Ea, VEa, and EDEA that are positive. This stands in contrast with
		McðmÞ.
DAB		Bond dissociation energy of AB.
DBEa		Electron affinity due to the attraction of the permanent dipole
		moment.
De		Minimum energy in a potential energy curve.
DeBA		Maximum value of A1 calculated from the DeBroglie wavelength
		of the electron. The value of ln(DeBA) is about 36 at 400 K.
eð Þ		Electron.
Ei		Activation energy for kinetic rate constant. Subscript 1 stands for
		attachment, 1 detachment, 2 dissociation, D recombination of
		electrons, N recombination of anions, ET electron transfer of ions,
E1=2		ET reverse of electron transfer.
		Polarographic half-wave reduction potential measured in aprotic
		solvents.
Ea		Electron affinity, energy between the most stable state of an anion
		in an electronic state and the most stable state of the neutra molecule.
Eabs		The maximum in the absorption spectra of negative ions.
EB		Formation of an anion by the impact of energetic electron beams.
ECD		Electron capture detector.
ECT		Absorption maximum for charge transfer complexes.
EDEA		The electron affinity of dissociating species minus the bond
		dissociation energy.
Eql(a/b)		Classification of compounds that form stable negative ions and
		have one or two temperature regions.
Eref		Reference potential for a specific reference electrode in polaro-
		graphic reduction potential determinations. The value for the
		saturated calomel electrode is 4.71 V.

GLOSSARY OF TERMS, ACRONYMS, AND SYMBOLS

333

EnCT

Endothermic charge transfer. Also called energetic ion beam

electron transfer.

Epd

Photodetachment energy, the energy difference between the anion

and the neutral in the geometry of the anion.

Err

Rearrangement energy, the Ea VEa.

ES

Electron swarm.

ET

Electron transmission, the electron current transmitted through a gas.

EvV

The value selected as the ‘‘best’’ current value. For measurements

of the same quantity with different methods, the least-squares best

value is the weighted average.

GPA

Gas phase acidity, also called the deprotonation energy of a

molecule, AH. It is

the energy for

the

reaction AH ¼ HðþÞ ¼

g( )

Að Þ.

functions

of (A(

)),

(A),

and

e( ); g(e(

))

¼

S(e

)

Partition

3=2

/h

3

(2p me kT)

. S is the spin

multiplicity of the

electron, the

other quantities are the fundamental constants, and T is the

temperature.

HIMPEC

Herschbach ionic Morse potential energy curves. A classification of

negative-ion potential energy curves originally proposed by

Herschbach and recently modified.

IP

Ionization potential.

Ib

Electron concentration in the absence of AB.

Ie

Electron concentration in the presence of AB.

kA

Dimensionless constant that modifies the attraction of the Morse

potential of anions.

kB

Dimensionless constant that modifies the exponent of the Morse

potential of anions.

kR

Dimensionless constant that modifies the repulsion of the Morse

potential of anions.

¼

k1

Rate

constant

for

thermal

electron

reaction,

k1

A1T 1=2

expð E1=RTÞ.

k 1 ¼ A 1T

k 1

Rate

constant

for

thermal electron detachment,

expð E 1=RTÞ.

k2

Rate constant for molecular ion dissociation, k2 ¼ A2T expð E2=

RTÞ.

kET

k ET

kD0 kD

Rate constant for electron transfer.

Rate constant for reverse electron transfer.

Rate constant for electron recombination.

Rate constant for electron recombination multiplied by positive-ion concentration.

334

kN0 kN

APPENDIX I

Rate constant for ion recombination.

Rate constant for ion recombination multiplied by positive-ion concentration.

KECD	ECD molar response. Subsequently just K.
Keq	Equilibrium constant for thermal electron reactions, Keq ¼ k1=k 1.
Le	Leaving group in dissociative electron attachment.
LUMO	Lowest unoccupied molecular orbital.
MðmÞ	Designation of HIMPEC with m ¼ 0 to 3. This indicates formation
	of a molecular ion in the Franck Condon region and the number of
	values of Ea, VEa, and EDEA that are positive. This contrasts with
	DðmÞ.
McðmÞ	Designation of HIMPEC with m ¼ 0 to 3. This indicates formation
	of a molecular ion in crossing the long-range curve and the number
	of values of Ea, VEa, and EDEA that are positive. This contrasts
	with DcðmÞ.
MCCI	Multiconfiguration configuration interaction. The modification of
	the wave functions used to calculate the energies utilizing semi-
	empirical calculations.
mddG	The solution energy difference for a reaction in polarographic
	determinations is G and depends on the solvent and specific
	reaction.
MGN	Magnetron method for measuring electron affinities.
n	Vibrational frequency in a Morse potential energy curve.
NIMS	Negative-ion mass spectrometry.
P	Positive ion.
PEa	Polarization electron affinity. The attraction is due to the polariz-
	ability of the molecule.
PD	Photodetachment, the removal of an electron from an ion by
	photons.
PES	Photoelectron spectroscopy, the measurement of the intensity and
	energy of electrons photodetached from an ion by a fixed-energy
	photon beam.
Precision	The reproducibility of a measurement. This is determined by
	random uncertainties, as opposed to systematic uncertainties.
P and A	A graph of two sets of values for the same quantity measured or
	calculated by two different methods. The deviations from a zero
	intercept unit slope line will identify systematic (inaccurate) and
	random (imprecise) uncertainties.
Qan	Ratio of the partition function of the anion to that of the neutral
	without the spin multiplicity term for the anion.
re, r	Internuclear distance r at the minimum of a potential energy curve.

	GLOSSARY OF TERMS, ACRONYMS, AND SYMBOLS	335
SCF	Self-consistent field quantum mechanical procedure.
Term symbol	The standard term symbol gives a pre-superscript of	2S þ 1,
	where S is the total spin. The major symbol is the total angular
	momentum. The post-superscript and subscript are a symmetry
	term and a spin orbital coupling term. The electronic configuration
	determines the term symbol.
Timeline	A chronological plot of values of a quantity measured with
	different techniques. The deviations from a constant value can be
	identified as random or systematic uncertainties to establish accu-
	racy and precision.
URX3O	Acronym for the optimization procedure of CURES-EC UHF, RHF,
	extremes, three(3), optimization. The UHF, RHF(3300), and
	RHF(0033) energies are calculated and compared to the experi-
	mental values. If the experimental value fits between the maximum
	and minimum values, then the agreement can be optimized.
UðABÞ	Morse potential energy curve for a molecule.
UðABð ÞÞ	Morse potential energy curve for the anion of AB.
VEa	Vertical electron affinity, energy difference between an anion in the
	geometry of the neutral molecule and the most stable state of the
	neutral.

Temperature Regions

From low (298 K) to high temperatures (600 K) these regions are as follows:

1.	The b region, where ðKN	ðk 1 þ k2ÞÞ and K ¼ k1=2kD
2.	The a region, where ðk 1	ðkN þ k2ÞÞ and K ¼ ½KN =2kD&½k1=k 1&
3.	The g region, where ðk2	kN Þ and ðk 1 k2Þ, and K ¼ ½k1k2=2kDk 1&
4.	The d region, where ðk2	ðk 1 þ kN ÞÞ and K ¼ k1=2kD

APPENDIX II

Structures of Organic Molecules

Names, Numbers, and Adiabatic Electron Affinities of

Bergman Dewar Set

Structure 1

336