Photochemical Recoil Spectroscopy

Diesen, R. W.; Wahr, J. C.; Adler, Samuel E.

doi:10.1063/1.1671600

Cited by 65 publications

(31 citation statements)

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“…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.…”

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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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confidence: 99%

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

Huang

et al. 2007

SCI CHINA SER B

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“…If Z has angular coordinates Om, CPm in the xyz system, then k = sinO m COSCPmel + sinOm sincpme2+ COScpme3. (5) 11L.12= IIL·k 12 can now be averaged over the molecular orientation, i.e., JdQ I Jl.1 2 f(Q, r). (6) In the present case the molecules are unoriented, i.e., f(Q, r) = 1/871"2 and the average over a is immediate:…”

Section: Theory Of the Anisotropic Flux In Photolysis Mappingmentioning

confidence: 99%

“…2 The phenomenon has been experimentally demonstrated by Solomon 3 through photolysis mapping, by Wilson and his students 4 through photofragment spectroscopy, and by Diesen, Wahr, and Adler. 5 Photolysis mapping is a detection method in which the anisotropic fragments are mapped onto a hemispherical surface by their anisotropic removal of a metallic mirror. Photofragment spectroscopy is a method used to measure both the energy and the angular distribution of the fragments resulting from the intersection of a pulsed light beam and a molecular beam.…”

Section: Introduction: Anisotropic Photodissociationmentioning

confidence: 99%

Photolysis Mapping Studies of Aliphatic Carbonyl Compounds

Solomon

Jonah

Chandra

et al. 1971

The Journal of Chemical Physics

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The photolysis mapping technique is a marriage of an old radical detecting system with the following principle: If polarized light is used for photodissociation, the fiux of fragments will be anisotropic because the molecular absorption is anisotropic in the molecular axis system. The simplest aliphatic carbonyl compounds (formaldehyde, acetaldehyde, propionaldehyde, and acetone) were photodissociated using polarized ultraviolet light. The gases were held at such a low pressure that the fragments travel to the walls without collision in the gas phase. On the walls the radicals were detected by the old mirror removal technique. There is a substantial anisotropy of removal. The sense of the anistropy is different for the different molecules, being perpendicular for formaldehyde and acetone, and parallel for acetaldehyde and propionaldehyde. These results are interpreted by assuming that the carbonyl compounds all become nonplanar in the excited state and the ultimate direction of the fragments can be inferred from the initial motion. In formaldehyde the departing hydrogen atom leaves in a direction perpendicular to the plane as does the methyl in acetone. On the other hand, in acetaldehyde and propionaldehyde the hydrogen atom leaves the molecular plane but remains attached to the central carbon atom while the departing alkyl radicals leave in the molecular plane, parallel to the transition dipole moment.

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“…40). Similar information on NO2 photolysis lifetimes and on product energy distributions stems frc)ni photofragment spectroscopy [41,421. I'rcdissociation linc widths at wavelengths near 397.9 nm havc been studied in rcf.…”

Section: Introductionmentioning

confidence: 99%

Primary Processes in the Photolysis of NO₂

Gaedtke

Troe

1975

Ber Bunsenges Phys Chem

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Etier(/ieuhrrtrayictig J Hohe Driickr / Phorochemie / Reaktionskint?tikThe quantum yield of the photolysis of NOz (6 Torr) under continuous irradiation has been measured in the presence of N z in the pressure range 0 I P(N,) I lo00 atm at temperatures 296 5 T 5 428 K and wavelengths 313 I 1 I 416 nm. The primary quantum yield is separated from the contribution of secondary reactions. The dependence of the primary quantum yield on pressure, temperature and wavelength is analyzed in terms of the specific rate constants k ( E ) for photolysis and detailed rate constants for collisonal energy transfer.Die Quantenausbeute der stationaren Photolyse von NO2 (6Torr) wurde in Gegenwart von N z im Druckbereich 0 2 P(N,) 5 IOOO atni bei Temperaturen 296 < T 5 428 K und Wellenlangen 313 5 i, 5 416 nm gernessen. Die primiire Quantenausbeute wird von den1 Beitrag der Folgereaktionen abgetrennt. Die Abhlngigkeit der primlren Quantenausbeute von Druck, Temperatur und Wellenllnge wird anhand der spezifischen Geschwindigkeitskonstanten k ( E ) f i r die Photolyse und von detaillierten Geschwindigkeitskonstanten f i r Energieubertragung in StoBen analysiert.

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Photochemical Recoil Spectroscopy

Cited by 65 publications

References 2 publications

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

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

Photolysis Mapping Studies of Aliphatic Carbonyl Compounds

Primary Processes in the Photolysis of NO₂

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Photochemical Recoil Spectroscopy

Cited by 65 publications

References 2 publications

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

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

Photolysis Mapping Studies of Aliphatic Carbonyl Compounds

Primary Processes in the Photolysis of NO2

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Primary Processes in the Photolysis of NO₂