Analysis of the ultrafast photodissociation of electronically excited CF2I2 molecules by femtosecond time-resolved photoelectron spectroscopy

Farmanara, P.; Stert, V.; Ritze, H.‐H.; Radloff, W.

doi:10.1063/1.481972

Cited by 16 publications

(9 citation statements)

References 13 publications

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“…The formation scheme of in which the minimum number of photons are absorbed is the (2 + 1‘) photon process, where the prime indicates the absorption of 264 nm pump photons; see Figure . Previous time-resolved ion imaging studies have shown that in the case of CF 3 I and CF 2 I 2 the photon schemes using the minimum number of photons are the dominant channels. , This was confirmed by coincidence imaging measurements 21 and time-resolved electron measurements . In the experiment we reduced the fluences of both the pump and probe laser to only produce the fragments of interest and to prevent photon processes involving more photons.…”

Section: Resultssupporting

confidence: 52%

Imaging of Ultrafast Molecular Elimination Reactions

2005

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Ultrafast molecular elimination reactions are studied using the velocity map ion imaging technique in combination with femtosecond pump-probe laser excitation. A pump laser is used to initiate the dissociative reaction, and after a predetermined time delay a probe laser "interrogates" the molecular system. Ionic fragments are detected with a two-dimensional velocity map imaging detector providing detailed information about the energetic and vectorial properties of mass selected photofragments. In this paper we discuss the ultrafast elimination of molecular iodine, I(2), from IF(2)C-CF(2)I, where the iodine atoms originate from neighboring carbon atoms. By varying the femtosecond delay between pump and probe pulse, it is found that elimination of molecular iodine is a concerted process, although the two carbon-iodine bonds are not broken synchronously. Energetic considerations suggest that the crucial step in this fragmentation process is an electron transfer between the two iodine atoms in the parent molecule, which leads to Coulombic attraction and the creation of an ion-pair state in the molecular iodine fragment.

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Section: Resultssupporting

confidence: 52%

Imaging of Ultrafast Molecular Elimination Reactions

2005

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“…23 Another possibility is that the initially excited state decays very rapidly into the lower-lying excited state similarly to what was proposed for the excited CF 2 I 2 molecule (30 fs decay). 24,25 An interpretation assigning the short-time dynamics at all probe wavelengths to the CH 2 Br radical is not consistent with the amount of excess vibrational energy stored in the radical immediately after the photodissociation. Since only about 14% of the total available energy in C-I breaking appears as vibrational excitation of the CH 2 Br radical 12 we expect that the hot CH 2 Br only contributes to the observed early-time dynamics at probe wavelengths shorter than ∼370 nm.…”

Section: Resultsmentioning

confidence: 97%

Ultrafast Study of the Photodissociation of Bromoiodomethane in Acetonitrile upon 266 nm Excitation

et al. 2002

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We studied the A-band photodissociation of bromoiodomethane, CH 2 BrI, in acetonitrile solution at room temperature by femtosecond pump-probe spectroscopy. Initiated by the 266 nm light, this reaction leads to the CH 2 Br-I isomer, most likely produced via in-cage recombination of the CH 2 Br and I photofragments. The isomer is formed vibrationally excited with a time constant of ∼7.5 ps and the hottest isomer molecules are observed as early as 1 ps after the UV excitation. Vibrational relaxation of the isomer molecules takes place on two distinct time scales of a few and ∼40 ps. The ground-state lifetime of the isomer is about 2.5 ns.

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“…30 The formation of molecular iodine is observed only upon excitation of CF 2 I 2 at 193 nm ͑6.5 eV͒. [33][34][35][36] In contrast to the gas-phase photochemistry, excitation of CF 2 I 2 in n-hexane with a single 350 nm photon ͑3.54 eV͒ leads to the ultrafast formation of molecular iodine in a 32% quantum yield. 37 Despite the fact that resonance Raman spectra of CF 2 I 2 are strongly solvent dependent, 38,39 the several picosecond build up of I 2 was observed in a wide range of solvents ͑methanol, acetonitrile, linear alkanes, and chlorinated alkanes͒.…”

Section: Introductionmentioning

confidence: 99%

Characterization of iso-CF2I2 in frequency and ultrafast time domains

El‐Khoury

George

Kalume

et al. 2010

The Journal of Chemical Physics

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The photolysis of diiododifluoromethane (CF(2)I(2)) in condensed phases was studied by a combination of matrix isolation and ultrafast time-resolved spectroscopy, in concert with ab initio calculations. Photolysis at wavelengths of 355 or 266 nm of CF(2)I(2):Ar samples (1:5000) held at approximately 8 K yielded iso-CF(2)I(2) (F(2)C-I-I), a metastable isomer of CF(2)I(2), characterized here for the first time. The infrared (IR) spectra of this isomer were recorded in matrix experiments, and the derived positions of the C-F stretching modes are in very good agreement with the predictions of high level ab initio calculations, which show that the iso-form is a minimum on the CF(2)I(2) ground state potential energy surface. The formation of this isomer following 350 nm excitation of CF(2)I(2) in room temperature CCl(4) solutions was monitored through its intense C-F stretching mode by means of ultrafast time-resolved IR absorption. Together, matrix isolation and ultrafast IR absorption experiments suggest that the formation of iso-CF(2)I(2) occurs via recombination of CF(2)I radical and I atom. Ultrafast IR experiments detect a delayed rise of iso-CF(2)I-I absorption, placing an upper limit of 400 fs for the C-I bond dissociation and primary geminate recombination processes. The product absorption spectrum recorded 1 ns after 350 nm excitation of CF(2)I(2) in solution is virtually identical to the visible absorption spectrum of iso-CF(2)I(2) trapped in matrix isolation experiments [with subtracted I(2)(X) absorption]. The formation of this isomer in solution at room temperature has direct dynamic implications for the ultrafast production of molecular iodine from electronically excited CF(2)I(2).

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Analysis of the ultrafast photodissociation of electronically excited CF2I2 molecules by femtosecond time-resolved photoelectron spectroscopy

Cited by 16 publications

References 13 publications

Imaging of Ultrafast Molecular Elimination Reactions

Imaging of Ultrafast Molecular Elimination Reactions

Ultrafast Study of the Photodissociation of Bromoiodomethane in Acetonitrile upon 266 nm Excitation

Characterization of iso-CF2I2 in frequency and ultrafast time domains

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