Dissociative electron attachment in nitrogen trifluoride

Sides, G. D.; Tiernan, T. O.

doi:10.1063/1.435079

Cited by 21 publications

(6 citation statements)

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“…Although NF 3 is a well-known electron scavenger, so far only dissociative attachment (DA) has been observed either in lowpressure 6 or in high-pressure 7 mass spectrometric studies.…”

Section: Introductionmentioning

confidence: 99%

Free Electron Attachment and Rydberg Electron Transfer to NF₃Molecules and Clusters

Ruckhaberle¹,

Lehmann²,

Matejčík³

et al. 1997

J. Phys. Chem. A

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Free electron attachment in the energy range 0−10 eV and Rydberg electron transfer (RET) to NF3 molecules, NF3 clusters, and NF3/Ar clusters are studied by means of negative ion mass spectrometry. The experimental results are compared with density functional theory (DFT) calculations. In the free electron experiment gas-phase NF3 generates the dissociative attachment (DA) products F-, F2 -, and NF2 - appearing from a broad resonance around 2 eV, in agreement with an earlier beam experiment. The most abundant fragment, F-, exhibits a small “threshold” signal at incident energies close to 0 eV. This signal increases with the target gas temperature and is due to transitions from the neutral to the anion involving vibrationally excited states close to the intersection between the two potential energy surfaces. From the temperature dependence of this threshold signal the activation energy for the exothermic DA reaction e- + NF3 → F- + NF2 is derived as E a = 0.1 ± 0.05 eV. Time-of-flight (TOF) analysis reveals that F- arises from a repulsive electronic state releasing the fragments with appreciable kinetic energy. Free electron attachment and RET to NF3 clusters produce undissociated cluster ions (NF3) n - including the monomer. In the case of free electrons they are still dominantly formed via the 2 eV resonance followed by intracluster relaxation processes. DFT calculations predict a lowering of the symmetry from C 3 v to C s on going from the neutral to the anion with one F atom substantially enlarged from the NF2 plane. The calculated (adiabatic) electron affinities are EA(NF3) = 1.71 eV and EA(NF2) = 1.18 eV. From the appearance energy in the DA experiment we derive EA(NF2) = 1.1 ± 0.1 eV.

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“…Although NF 3 is a well-known electron scavenger, so far only dissociative attachment (DA) has been observed either in lowpressure 6 or in high-pressure 7 mass spectrometric studies.…”

Section: Introductionmentioning

confidence: 99%

Free Electron Attachment and Rydberg Electron Transfer to NF₃Molecules and Clusters

Ruckhaberle¹,

Lehmann²,

Matejčík³

et al. 1997

J. Phys. Chem. A

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“…The appearance potential of Ffrom NF3 is very near 0 eV (11), and previous experiments in our laboratory have demonstrated that the rate coefficient for attachment of near-thermal electrons to NF3, yielding F-, was very large (12). The F-ion was selected for investigation as a NICI reagent ion for several reasons.…”

Section: Introductionmentioning

confidence: 99%

Formation and Reactions of Negative Ions Relevant to Chemical Ionization Mass Spectrometry. I. CI Mass Spectra of Organic Compounds Produced by F - Reactions

Tiernan¹,

Chang²,

Cheng³

1980

Environmental Health Perspectives

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A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F(-) with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F(-) reagent ion was generated from CF(3)H or NF(3), typically at an ion source pressure of 100 mum. In pure NF(3), F(-) is the major ion formed and constitutes more than 90% of the total ion intensity. While F(-) is also the major primary ion formed in pure CF(3)H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)(n)F(-) (n = 1-3) ions, which makes CF(3)H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M - 1)(-) ion was observed in the F(-) chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)(-) ions upon reaction with F(-). A weaker (M + F)(-) ion was also detected in the F(-) chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F(-) chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO(-), X(-), CN(-), NO(2) (-), and OR(-), respectively. In addition, esters show a very weak (M - 1)(-) ion (except formates). In the F(-) chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)(-) ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F(-) ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several experimental parameters, including source pressure, relative proportions of the reagent and analyte, and other ion source parameters, on the observed chemical ionization mass spectra were also investigated. In a mixture of NF(3) and n-butanol, for example, the ratio of the intensities of the ions characteristic of the alcohol to that of the (HF)(n)F(-) ion was found to decrease with increasing sample pressure, with increasing NF(3) pressure, and with increasing electron energy. No significant effects on the spectra were observed to result from variation of the source repeller field or the source temperature. The addition of argon to the source as a potential moderator did not alter the F(-) chemical ionization spectrum significantly, but the use of oxygen appears to inhibit formation of the (HF)(n)F(-) cluster ion. The advantages of using F(-) as a chemical ionization reagent are discussed, and comparisons are made with other reagent ions.

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“…First, it was expected that F-could be readily produced in large abundance by electron impact on molecules such as CH3F and NF3. The appearance potential of F-from NF3 is very near 0 eV (11), and previous experiments in our laboratory have demonstrated that the rate coefficient for attachment of near-thermal electrons to NF3, yielding F-, was very large (12). Also, Fis the only ionic product observed from low energy electron attachment to NF3.…”

Section: Introductionmentioning

confidence: 59%

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. Cl mass spectra of organic compounds produced by F ⁻ reactions

Tiernan¹,

Chang²,

Cheng³

1980

Environ Health Perspect

Self Cite

View full text Add to dashboard Cite

A systematic study of the negative-ion chemical ionization mass spectra produced by the reaction of F− with a wide variety of organic compounds has been accomplished. A time-of-flight mass spectrometer fitted with a modified high pressure ion source was employed for these experiments. The F− reagent ion was generated from CF3H or NF3, typically at an ion source pressure of 100 μm. In pure NF3, F− is the major ion formed and constitutes more than 90% of the total ion intensity. While F− is also the major primary ion formed in pure CF3H, it undergoes rapid ion-molecule reactions at elevated source pressures, yielding (HF)nF− (n = 1−3) ions, which makes CF3H less suitable as a chemical ionization reagent gas. Among the organic compounds investigated were carboxylic acids, ketones, aldehydes, esters, alcohols, phenols, halides, nitriles, nitrobenzene, ethers, amines and hydrocarbons. An intense (M − 1)− ion was observed in the F− chemical ionization mass spectra of carboxylic acids, ketones, aldehydes and phenols. Alcohols yield only (M + F)− ions upon reaction with F−. A weaker (M + F)− ion was also detected in the F− chemical ionization spectra of carboxylic acids, aldehydes, ketones and nitriles. The F− chemical ionization mass spectra of esters, halides, nitriles, nitrobenzene and ethers are characterized primarily by the ions, RCOO−, X−, CN−, NO2−, and OR−, respectively. In addition, esters show a very weak (M − 1)− ion (except formates). In the F− chemical ionization spectra of some aliphatic alkanes and o-xylene, a very weak (M + F)− ion was observed. Amines and aliphatic alkenes exhibit only insignificant fragment ions under similar conditions, while aromatic hydrocarbons, such as benzene and toluene are not reactive at all with the F− ion. The mechanisms of the various reactions mentioned are discussed, and several experimental complications are noted. In still other studies, the effects of varying several experimental parameters, including source pressure, relative proportions of the reagent and analyte, and other ion source parameters, on the observed chemical ionization mass spectra were also investigated. In a mixture of NF3 and n-butanol, for example, the ratio of the intensities of the ions characteristic of the alcohol to that of the (HF)nF− ion was found to decrease with increasing sample pressure, with increasing NF3 pressure, and with increasing electron energy. No significant effects on the spectra were observed to result from variation of the source repeller field or the source temperature. The addition of argon to the source as a potential moderator did not alter the F− chemical ionization spectrum significantly, but the use of oxygen appears to inhibit formation of the (HF)nF− cluster ion. The advantages of using F− as a chemical ionization reagent are discussed, and comparisons are made with other reagent ions.

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Dissociative electron attachment in nitrogen trifluoride

Abstract: The rate constant for the dissociative attachment of thermal elections (300−350 °K) to nitrogen trifluoride has been measured using a flowing afterglow technique. (AIP)

Cited by 21 publications

References 21 publications

Free Electron Attachment and Rydberg Electron Transfer to NF₃Molecules and Clusters

Free Electron Attachment and Rydberg Electron Transfer to NF₃Molecules and Clusters

Formation and Reactions of Negative Ions Relevant to Chemical Ionization Mass Spectrometry. I. CI Mass Spectra of Organic Compounds Produced by F - Reactions

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. Cl mass spectra of organic compounds produced by F ⁻ reactions

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Dissociative electron attachment in nitrogen trifluoride

Abstract: The rate constant for the dissociative attachment of thermal elections (300−350 °K) to nitrogen trifluoride has been measured using a flowing afterglow technique. (AIP)

Cited by 21 publications

References 21 publications

Free Electron Attachment and Rydberg Electron Transfer to NF3Molecules and Clusters

Free Electron Attachment and Rydberg Electron Transfer to NF3Molecules and Clusters

Formation and Reactions of Negative Ions Relevant to Chemical Ionization Mass Spectrometry. I. CI Mass Spectra of Organic Compounds Produced by F - Reactions

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. Cl mass spectra of organic compounds produced by F − reactions

Contact Info

Product

Resources

About

Free Electron Attachment and Rydberg Electron Transfer to NF₃Molecules and Clusters

Free Electron Attachment and Rydberg Electron Transfer to NF₃Molecules and Clusters

Formation and reactions of negative ions relevant to chemical ionization mass spectrometry. I. Cl mass spectra of organic compounds produced by F ⁻ reactions