Photodissociation channels and energy partitioning in the photofragmentation of alkyl iodides

Zhu, Qihe; Cao, Jing; Wen, Y.; Zhang, Jianming; Zhong, Xian; Huang, Yuhui; Fang, W.Q.; Wu, Xiaojun

doi:10.1016/0009-2614(88)87301-9

Cited by 55 publications

(40 citation statements)

References 20 publications

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“…In addition, the values of V E are smaller than those of corresponding int E , mainly due to the rotational excitation of the photofragment C 2 H 5 . Furthermore, we have compared our energy partitioning int avl / E E results with some published results in [7,14,25,26]. Because of the higher resolution of our PTS, giving many separated vibrational peaks, (while in other work, giving only a contour without vibrational peaks,) our int avl / E E results seem to be more reliable.…”

Section: Resultsmentioning

confidence: 47%

“…Berkeley [4] . At the same time, similar experimental set-ups were built in the University of Manchester [5] and in our laboratory [6,7] . This kind of experimental apparatus is still used in many laboratories.…”

mentioning

confidence: 99%

“…In the 200-320 nm region, the excitation of C 2 H 5 I is assigned to the * n σ → transition, giving photodissociation. The photodissociation channel ratio has been studied with different methods, such as the laser-induced fluorescence (LIF) [18,19] , PTS [7,12] , etc. I*( 2 P 1/2 )/I( 2 P 3/2 ) is controlled by the excitation probability to the 3 Q 0 , 3 Q 1 , 1 Q 1 excited states and the curve crossing between 3 Q 0 and 1 Q 1 during the dissociation process [12] .…”

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confidence: 99%

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High-resolution photofragment translational spectroscopy for the UV photodissociation of C2H5I

Huang

et al. 2007

SCI CHINA SER B

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The photodissociation of ethyl iodide at 279.71, 281.73, 304.02 and 304.67 nm has been studied on our new mini-photofragment translational spectrometer with a total flight path of only 5 cm. Some vibrational peaks are firstly resolved in the TOF spectra of I*( 2 P 1/2 ) and I( 2 P 3/2 ) channels. These vibrational peaks are assigned to the excitation states (ν 2 = 0, 1, 2,…) of the umbrella mode (ν 2 , 540 cm −1 ) of the photofragment C 2 H 5 , and the distribution of the vibrational states is obtained. The dissociation energy has been determined to be D 0 (C-I)=2.314 ± 0.03 eV. The energy partitioning of the available energy (E avl =E T +E int =E T +E V,R ) calculated from our experimental data / int avl E E = 22.1% at 281.73 nm, 22.4% at 304.02 nm for the I* channel, and / int avl E E = 25.2% at 279.71 nm, 25.9% at 304.67 nm for the I channel, seem to be more reliable. photofragment translational spectroscopy, C 2 H 5 I, photodissociation, vibrational state distribution, energy partitioning，dissociation energyFor the photodissociation of molecules, photofragment translational spectroscopy offers a way to study the dynamics of photodissociation in a collision-free regime [1] . Analysis of the velocity distribution and the angular distribution of the photofragments can give information of the potential energy surfaces, the energy partitioning, the vibrational state distribution of the photofragments, the dissociation energy, the life time of the excitation state and the curve-crossing. The original photofragment translational spectrometer (PTS) [2,3] was with the structure that the molecular beam, the laser, and the detection axis were perpendicular to each other. The improved PTS, with the molecular beam rotatable, was called the "Rotating Source Machine" at Yuan Lee's Lab in U.C. Berkeley [4] . At the same time, similar experimental set-ups were built in the University of Manchester [5] and in our laboratory [6,7] . This kind of experimental apparatus is still used in many laboratories. Some high resolution experimental results have been obtained [8,9] , but the apparatus is very complicated and in need of ultra-high vacuum up to 10 −8 Pa. At present, the ion imaging apparatus, originally designed by Chandler and Houston [10] , and improved by Eppink and Parker [11] , is used more often. From the ion image, the angular distribution of the photofragments can be obtained simultaneously with the high-resolution velocity distribution, but high-grade uniform Micro Channel Plates (MCP) and CCD camera are required. We have built a simple and small photofragment translational spectrometer of only 5 cm total flight path and used a simple MCP as the detector. However, the resolution of this PTS is high enough to resolve some vibrational states of the photofragments.Alkyl halides have been concerned to the atmospheric chemistry due to their role in ozone depletion. The photodissociation of ethyl iodide (C 2 H 5 I) has been widely studied [12][13][14][15][16][17][18][19] . The absorption cross-section of C 2 H 5 I was meas...

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Section: Resultsmentioning

confidence: 47%

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confidence: 99%

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confidence: 99%

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High-resolution photofragment translational spectroscopy for the UV photodissociation of C2H5I

Huang

et al. 2007

SCI CHINA SER B

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“…We used the normal-mode coefficients and the appropriate parameters of Table 4 in Eqns (8) and (9) to Ðnd the expectation value for each Table 1. Wavenumbers (m8 ) of modes observed in A-band resonance Raman spectra of 2-iodopropane and tert-butyl iodide…”

Section: Resultsmentioning

confidence: 99%

“…This result Ó shows a correlation with the amount of internal energy found in the radical photoproducts and the widths of their internal energy distributions as measured by timeof-Ñight photofragment spectroscopy. For instance, the reported fraction of the available energy appearing as internal excitation of the radical ranges from 28 to 38% in iodoethane1, 5,8,29 and from 43 to 67% in 2-iodopropane.1,6,8 Hence both the short-time and the long-time dynamics suggest that less of the absorbed photon energy goes into breaking the CÈI bond with more energy partitioned to distort the rest of the molecule in 2-iodopropane than in iodoethane. This is an interesting result since it is not clear to what extent, in general, the very short-time dynamics determine the Ðnal partitioning of the available energy in a photodissociation process.…”

Section: Discussionmentioning

confidence: 96%

Short-time photodissociation dynamics of iodoalkanes: refinement using resonance Raman intensities of isotopic derivatives

Phillips

Myers

1997

J. Raman Spectrosc.

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Resonance Raman spectra of and iodide in cyclohexane solution were 1,1,1,3,3,3-d 6 -2-iodopropane d 9 -tert-butyl obtained at excitation wavelengths of 266 and 217.8 nm. The 266 nm spectra, resonant with the directly dissociative A-state absorption, display long overtone progressions in the nominal C-I stretch (ca. 500 cm-1) and some intensity in fundamentals, overtones and combination bands of bending and C-C stretching modes. The 266 nm resonance Raman intensities and the A-band absorption spectrum are simultaneously modelled using wavepacket propagation on a multidimensional locally harmonic potential surface. The dimensionless normal coordinate wavepacket motions determined from the simulations are converted into internal coordinate motions by making use of previous results on the isotopically unsubstituted compounds to remove some of the indeterminacy in the signs of the normal mode displacements. In the Ðrst 10 fs the CÈI bond lengthens less in these higher alkanes than in iodoethane, suggesting that more of the available energy goes toward CÈI bond cleavage in iodoethane.

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QCT study of the vibrational and translational role in the H + C2H6(ν1, ν2, ν5, ν7, ν9 and ν10) reactions

Espinosa‐García

Calle-Cancho²,

Corchado

2019

Theor Chem Acc

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Photodissociation channels and energy partitioning in the photofragmentation of alkyl iodides

Cited by 55 publications

References 20 publications

High-resolution photofragment translational spectroscopy for the UV photodissociation of C2H5I

High-resolution photofragment translational spectroscopy for the UV photodissociation of C2H5I

Short-time photodissociation dynamics of iodoalkanes: refinement using resonance Raman intensities of isotopic derivatives

QCT study of the vibrational and translational role in the H + C2H6(ν1, ν2, ν5, ν7, ν9 and ν10) reactions

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