58 research outputs found
Spectroscopy of free radicals and radical containing entrance-channel complexes in superfluid helium nano-droplets
The spectroscopy of free radicals and radical containing entrance-channel
complexes embedded in superfluid helium nano-droplets is reviewed. The
collection of dopants inside individual droplets in the beam represents a
micro-canonical ensemble, and as such each droplet may be considered an
isolated cryo-reactor. The unique properties of the droplets, namely their low
temperature (0.4 K) and fast cooling rates ( K s) provides
novel opportunities for the formation and high-resolution studies of molecular
complexes containing one or more free radicals. The production methods of
radicals are discussed in light of their applicability for embedding the
radicals in helium droplets. The spectroscopic studies performed to date on
molecular radicals and on entrance / exit-channel complexes of radicals with
stable molecules are detailed. The observed complexes provide new information
on the potential energy surfaces of several fundamental chemical reactions and
on the intermolecular interactions present in open-shell systems. Prospects of
further experiments of radicals embedded in helium droplets are discussed,
especially the possibilities to prepare and study high-energy structures and
their controlled manipulation, as well as the possibility of fundamental
physics experiments.Comment: 25 pages, 12 figures, 4 tables (RevTeX
A high-resolution infrared spectroscopic investigation of the halogen atom-HCN entrance channel complexes solvated in superfluid helium droplets
Rotationally resolved infrared spectra are reported for the X-HCN (X = Cl,
Br, I) binary complexes solvated in helium nanodroplets. These results are
directly compared with that obtained previously for the corresponding X-HF
complexes [J. M. Merritt, J. K\"upper, and R. E. Miller, PCCP, 7, 67 (2005)].
For bromine and iodine atoms complexed with HCN, two linear structures are
observed and assigned to the and ground
electronic states of the nitrogen and hydrogen bound geometries, respectively.
Experiments for HCN + chlorine atoms give rise to only a single band which is
attributed to the nitrogen bound isomer. That the hydrogen bound isomer is not
stabilized is rationalized in terms of a lowering of the isomerization barrier
by spin-orbit coupling. Theoretical calculations with and without spin-orbit
coupling have also been performed and are compared with our experimental
results. The possibility of stabilizing high-energy structures containing
multiple radicals is discussed, motivated by preliminary spectroscopic evidence
for the di-radical Br-HCCCN-Br complex. Spectra for the corresponding molecular
halogen HCN-X complexes are also presented.Comment: 20 pages, 15 figures, 6 tables, RevTe
Entrance Channel X-HF (X=Cl, Br, and I) Complexes studied by High-Resolution Infrared Laser Spectroscopy in Helium Nanodroplets
Rotationally resolved infrared spectra are reported for halogen atom - HF
free radical complexes formed in helium nanodroplets. An effusive pyrolysis
source is used to dope helium droplets with Cl, Br and I atoms, formed by
thermal dissociation of Cl, Br and I. A single hydrogen fluoride
molecule is then added to the droplets, resulting in the formation of the X-HF
complexes of interest. Analysis of the resulting spectra confirms that the
observed species have ground electronic states, consistent with
the linear hydrogen bound structures predicted from theory. Stark spectra are
also reported for these species, from which the permanent electric dipole
moments are determined.Comment: 41 pages, 16 figures, 5 table
C–C Stretching Raman Spectra and Stabilities of Hydrocarbon Molecules in Natural Gas Hydrates: A Quantum Chemical Study
Steroid Non-Responsive Optic Neuropathy (Presentation Video)
Loss of vision OUA 75-year old with painless, progressive loss of vision. Previous history significant for BPH and excised skin malignant melanoma.VA: Initial - 20/50 OD, 20/25 OS; Color plates: 6/12 OD, 12/12 OS; Follow-up - 20/70 OD, 20/120 OS; Color plates: 1/12 OD, 0/12 OS; RAPD OSMRIGlomeruloid vascular proliferation; Cells positive for glial fibrillary astrocytic protein consistent with glioblastoma multiforme.Corticosteroids; Surgery; XRT1. Millar WS, Tartaglino LM, Sergott RC, Freidman DP and Flanders AE: MR of Malignant Optic Glioma of Adulthood. AJNR 16:1673-1676, 1995. 2. Freidman DP and Hollander MD: Neuroradiology Case of the Day. RadioGraphics 18: 1046-1048, 1998. 3. Wabbels B, Demmler A, Seitz J et al: Unilateral adult malignant optic nerve glioma. Graefe's Arch Clin Exp Ophthalmol 242:741-748, 2004. 4. Hoyt WF, Meshel LG, Lessell S and al:Malignant Optic Glioma of Adulthood. Brain 96: 121-132, 1973
10th Meeting of the European Neuro-Ophthalmology Society, Barcelona, Spain, June 18-21, 2011
Steroid Non-Responsive Optic Neuropathy (PowerPoint)
Loss of vision OUA 75-year old male with painless, progressive loss of vision. Previous history significant for BPH and excised skin malignant melanoma.VA: Initial - 20/50 OD, 20/25 OS; color plates: 6/12 OD, 12/12 OS; Follow-up - 20/70 OD, 20/120 OS; Color plates: 1/12 OD, 0/12 OS; RAPD OSMRIGlomeruloid vascular proliferation; Cells positive for glial fibrillary astrocytic protein consistent with glioblastoma multiforme.Corticosteroids; Surgery XRT1. Millar WS, Tartaglino LM, Sergott RC, Freidman DP and Flanders AE: MR of Malignant Optic Glioma of Adulthood. AJNR 16:1673-1676, 1995. 2. Freidman DP and Hollander MD: Neuroradiology Case of the Day. RadioGraphics 18: 1046-1048, 1998. 3. Wabbels B, Demmler A, Seitz J et al: Unilateral adult malignant optic nerve glioma. Graefe's Arch Clin Exp Ophthalmol 242:741-748, 2004. 4. Hoyt WF, Meshel LG, Lessell S and al:Malignant Optic Glioma of Adulthood. Brain 96: 121-132, 1973
Steroid Non-Responsive Optic Neuropathy
Loss of vision OUA 75-year old male with painless, progressive loss of vision. Previous history significant for BPH and excised skin malignant melanoma.VA: Initial - 20/50 OD, 20/25 OS; Color plates: 6/12 OD, 12/12 OS; Follow-up - 20/70 OD, 20/120 OS; Color plates: 1/12 OD, 0/12 OS; RAPD OSMRIGlomeruloid vascular proliferation; Cells positive for glial fibrillary astrocytic protein consistent with glioblastoma multiforme.Corticosteroids; Surgery; XRT1. Millar WS, Tartaglino LM, Sergott RC, Freidman DP and Flanders AE: MR of Malignant Optic Glioma of Adulthood. AJNR 16:1673-1676, 1995. 2. Freidman DP and Hollander MD: Neuroradiology Case of the Day. RadioGraphics 18: 1046-1048, 1998. 3. Wabbels B, Demmler A, Seitz J et al: Unilateral adult malignant optic nerve glioma. Graefe's Arch Clin Exp Ophthalmol 242:741-748, 2004. 4. Hoyt WF, Meshel LG, Lessell S and al:Malignant Optic Glioma of Adulthood. Brain 96: 121-132, 1973
Hard to Get (Presentation Video)
Loss of vision OD; Right-sided headacheA 77-year old male with headache and visual loss OD. Previous history significant for hypertension, ischemic heart disease, basal cell carcinoma and invasive transitional cell carcinoma Tx cystectomy and chemotherapy.VA: CF OD, 20/25 OS declining to NLP OD, 20/30 OD: Color plates: none OD, 14/14 OS; RAPD ODCT; MRIClusters of atypical cells with epithelial features and mitoses consistent with carcinoma.IV and oral corticosteroids; Antineoplastic agentsN/
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