About the photoionization of methyl bromide (CH3Br). Photoelectron and photoionization mass spectrometric investigation

Locht, Robert; Leyh, Bernard; Dehareng, Dominique; Hottmann, K.; Jochims, H.‐W.; Baumgärtel, H.

doi:10.1016/j.chemphys.2005.10.006

Cited by 16 publications

(36 citation statements)

References 38 publications

(112 reference statements)

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“…Yet these ion-pair states are crossing Rydberg states converging on the C 2 A 1 state of CH 3 X + where an electron has been excited from the 2a 1 molecular orbital which has more C−H than C−X σ-character. 4,5,6,8 Thus excitation of this electron might be expected to weaken the C−H σ-bond to a greater extent.…”

Section: − From Ch 3 X Between 16−24 Evmentioning

confidence: 99%

“…For CH 3 Cl and CH 3 Br, the 3p / 4p π-orbitals of Cl / Br show little mixing with the CH 3 X σ-orbitals where the evidence is best provided from HeI, HeII or threshold photoelectron spectroscopy. [4][5][6][7] Both molecules show the effects of spin-orbit splitting, but limited vibrational structure in the (2e) −1 first band with a strong v + =0 transition, showing that the electron has been removed from an orbital that is essentially non-bonding in character. By contrast, the first photoelectron band of CH 3 F shows no measurable spin-orbit splitting, but an extended vibrational progression.…”

Section: Ae(a − ) ≥ Ie(ab) + D O (A−b + ) − Ea(a) (Ii)mentioning

confidence: 99%

“…The sensitivity of the ionisation gauge to CH 3 X (X = F,Cl,Br), SF 6 and CF 4 , which is essential for determination of absolute cross sections of anion formation, was calibrated in a separate experiment relative to N 2 using a capacitance manometer. 20 Gas samples were supplied by Apollo Scientific or Aldrich Chemical Company, and were used without further purification.…”

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confidence: 99%

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Vacuum-UV negative photoion spectroscopy of CH3F, CH3Cl and CH3Br

Rogers

Tuckett

Dunn

et al. 2010

Phys. Chem. Chem. Phys.

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Using tunable vacuum-UV radiation from a synchrotron, negative ions are detected by quadrupolar mass spectrometry following photoexcitation of three gaseous halogenated methanes CH 3 X (X = F,Cl,Br). The In common with many quadrupoles, the spectra of m/z 1 (H − ) anions show contributions from all anions, and only for CH 3 Br is it possible to perform the necessary subtraction to obtain the true H − spectrum.The anion cross sections are normalised to vacuum-UV absorption cross sections to obtain quantum yields for their production. The appearance energies of X − and CH 2 X − are used to calculate upper limits to 298 K bond dissociation energies for D o (H 3 C−X) and D o (XH 2 C−H) which are consistent with literature values. The spectra suggest that most of the anions are formed indirectly by crossing of Rydberg states of the parent molecule onto an ion-pair continuum. The one exception is the lowestenergy peak of F − from CH 3 F at 13.4 eV, where its width and lack of structure suggest it may correspond to a direct ion-pair transition.

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Section: − From Ch 3 X Between 16−24 Evmentioning

confidence: 99%

Section: Ae(a − ) ≥ Ie(ab) + D O (A−b + ) − Ea(a) (Ii)mentioning

confidence: 99%

mentioning

confidence: 99%

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Vacuum-UV negative photoion spectroscopy of CH3F, CH3Cl and CH3Br

Rogers

Tuckett

Dunn

et al. 2010

Phys. Chem. Chem. Phys.

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“…In the recent past, we thoroughly investigated several molecular systems, e.g. the monohalogenated derivatives of methane CH 3 F [1][2][3][4][5], CH 3 Cl [6][7][8] and CH 3 Br [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

The vacuum UV photoabsorption spectroscopy of vinyl fluoride (C2H3F): The vibrational fine structure and its analysis

et al. 2009

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The vacuum UV photoabsorption spectrum of C 2 H 3 F has been examined in detail between 6 eV and 25 eV photon energy by using synchrotron radiation. The analysis of the data is supported by ab initio quantum mechanical calculations applied to valence and Rydberg excited states of C 2 H 3 F. At 7.6 eV the π → π * and the 2a" → 3s transitions are observed. An analysis is proposed and applied to the mixed fine structure belonging to these transitions. For the π → π * transition one single long vibrational progression is observed with hcω e = 95 ± 7 meV (766 ± 56 cm -1 ) and its adiabatic excitation energy is 6.892 eV (55 588 cm -1 ). The 2a" → 3s transition is characterized by a single short progression with hcω e = 167 ± 10 meV (1350 ± 80 cm -1 ) starting at 6.974 eV (56 249 cm -1 ). From the present ab initio calculations these two wavenumbers best correspond to the vibrational modes υ 9 (CH 2 rock in-plane, FCC-bend) and υ 6 (CH 2 rock in-plane, CF stretch) calculated at 615 cm -1 in the π * state and 1315 cm -1 in the ( 2 A")3s Rydberg state respectively. The C=C stretching could not be excluded. The dense structured spectrum observed between 8.0 eV and 10.5 eV has been analyzed in terms of vibronic transitions to Rydberg states all converging to the C 2 H 3 F + (X A") ionic ground state. An analysis of the associated complex fine structure of the individual Rydberg states has been attempted providing average values of the wavenumbers, e.g., for the ( 2 A")3p Rydberg state hcω 9 = 60 ± 1 meV (or 484 ± 8 cm -1 ), hcω 7 = 151 ± 7 meV (or 1218 ± 60 cm -1 ), hcω 4 = 191 ± 3 meV (or 1540 ± 24 cm -1 ). The assignment of hcω = 105 ± 5 meV (or 823 ± 40 cm -1 ) is discussed. These experimental values are in good agreement with the theoretical predictions for C 2 H 3 F + [R. Locht, B. Leyh, D. Dehareng, K. Hottmann, H. Baumgärtel, Chem. Phys. (in press)]. Above 10.5 eV and up to 25 eV several broad and strong bands are tentatively assigned to transitions to valence (V-V) and/or Rydberg (V-R) states converging to excited ionic states of C 2 H 3 F.

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“…During the last decade our laboratory paid a lot of attention to the V-UV spectroscopy, the photoelectron spectroscopy [Threshold (TPES), Constant Ion State (CIS) and He-I] and the mass spectro-metric photoionization of the monohalogenated derivatives of methane, i.e., CH 3 F [14][15][16][17], CH 3 C1 [18][19][20], and recently CH 3 Br [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Medium and high resolution vacuum UV photoabsorption spectroscopy of methyl iodide (CH3I) and its deuterated isotopomers CD3I and CH2DI. A Rydberg series analysis

et al. 2009

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The vacuum UV photoabsorption spectrum of CH 3 I has been investigated between 5 eV and 20 eV. Numerous vibronic transitions are observed. In the high 10-20 eV photon energy range weak to very weak diffuse bands are observed and ascribed to electronic transitions from 3a 1 , 1e and 2a 1 to Rydberg orbitals. In the 6-10.5 eV photon energy range more than 200 sharp and strong to weak lines have been observed. Several photon energy ranges were explored under high resolution conditions allowing us to observe many series up to high values of the principal quantum number n. They are assigned to vibration-less Rydberg transitions and classified into two groups converging to the two components of the spin-orbit split X 2 E state of CH 3 I + . These two groups consist of six different Rydberg series, i.e., nsa 1 , npa 1 , npe, nda 1 , nde and nf. A very close correlation has been established between the term values of the Rydberg states in CH 3 I and in Xe for ns, np, nd and nf Rydberg transitions. For the first time, the same measurements have been performed and the interpretation has been proposed for the photoabsorption spectrum of CH 2 DI and CD 3 I in the 6-10.5 eV photon energy range. For these two species, ionization energies are deduced: for the X 2 E 3/2 and X 2 E 1/2 states of CH 2 DI, these are IE ad = 9.544 eV and IE ad = 10.168 eV, respectively, and the corresponding energies are 9.552 eV and 10.173 eV in CD 3 I.

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About the photoionization of methyl bromide (CH3Br). Photoelectron and photoionization mass spectrometric investigation

Cited by 16 publications

References 38 publications

Vacuum-UV negative photoion spectroscopy of CH3F, CH3Cl and CH3Br

Vacuum-UV negative photoion spectroscopy of CH3F, CH3Cl and CH3Br

The vacuum UV photoabsorption spectroscopy of vinyl fluoride (C2H3F): The vibrational fine structure and its analysis

Medium and high resolution vacuum UV photoabsorption spectroscopy of methyl iodide (CH3I) and its deuterated isotopomers CD3I and CH2DI. A Rydberg series analysis

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