Excimer

About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.

A new blue‐green excimer laser in XeF

Abstract: A new blue‐green excimer laser has been demonstrated on the C‐A transition in XeF, with an output energy of greater than 1 mJ Xe*2 excimer fluorescence at 172 nm was used to photodissociate XeF2, producing XeF[B (1/2)] and XeF[C (3/2)] The B (1/2) state was collisionally relaxed to the C (3/2) state with an Ar buffer Lasing then occurs sequentially on the B (1/2) ‐X (1/2) and C (3/2) ‐A (3/2) transitions Measurements of the C‐A laser spectrum showed a peak wavelength of 483 nm with a bandwidth of 12 nm This new laser is potentially highly efficient and scalable and should be tunable over a bandwidth greater than 40 nm

Excimer/Exciplex Formation in van der Waals Dimers of Aromatic Molecules

Abstract: Van der Waals dimers between benzofuran, dibenzofuran, and fluorene were studied in a supersonic jet. These show red-shifted excimer/exciplex emission following excitation to their locally excited states. The dibenzofuran dimer forms an excimer from its zero-point level, while the dibenzofuran−benzofuran and fluorene−benzofuran dimers require a moderate amount of excess vibrational energy for excimer formation. Exciplex formation in dibenzofuran−fluorene was inferred from spectral broadening. Excimer/exciplex formation was attributed to strong mixing of a charge transfer state with the exciton state. The charge transfer state has a low enough energy at its equilibrium geometry to mix, but this requires a large change in geometry from the equilibrium geometry of the locally excited state. There is a barrier in the adiabatic potential surface between the minima of the locally excited state and the excimer/exciplex state. This barrier is larger for greater differences in equilibrium geometry.

One-year results of excimer laser photorefractive keratectomy for myopia.

Abstract: BACKGROUND Excimer laser photorefractive keratectomy for the correction of myopia is presently under investigation in the United States by the Food and Drug Administration (FDA). The Phase II-B FDA study is being conducted on 75 normally sighted myopic eyes utilizing three currently available excimer lasers. This report presents the 1-year results on 12 myopic eyes treated with the VISX excimer laser system at the Ellis Eye Center at Cedars-Sinai Medical Center in Los Angeles under the Phase II-B FDA protocol. METHODS Twelve eyes of 12 patients with myopia between -1.75 and -5.00 diopters underwent 193 nm argon/fluoride excimer laser photorefractive keratectomy. The epithelium was mechanically removed, and fixation was accomplished with a suction ring which provided nitrogen flow across the corneal surface. The computer controlled corneal ablations were 5.00 mm in diameter and were accomplished with an iris diaphragm closing from large to small. RESULTS The preoperative spherical equivalent myopia was -3.50 D (SD = 1.02) and the postoperative myopia was -0.25 (SD = 0.48). Eleven of the 12 patients achieved an uncorrected visual acuity of 20/30 or better and were corrected to within +/- 0.50 D of emmetropia. All corneas demonstrated a mild reticular subepithelial haze which was barely visible at 1 year. There were no vision-threatening complications and none of the eyes experienced a loss of best corrected visual acuity. CONCLUSIONS In this small trial, the excimer laser appears to be capable of accurately changing the refractive power of the cornea for the correction of myopia with minimal side effects. Only when larger numbers of patients undergo the procedure will we be able to determine the safety and efficacy of photorefractive keratectomy as a refractive surgical procedure.

Pyrene–Oxadiazoles for Organic Light-Emitting Diodes: Triplet to Singlet Energy Transfer and Role of Hole-Injection/Hole-Blocking Materials

Abstract: Three pyrene–oxadiazole derivatives were synthesized and characterized by optical, electrochemical, thermal, and theoretical investigations to obtain efficient multifunctional organic light emitting diode (OLED) materials. Synthesized molecules were used as emitters and electron transporters in three different device configurations, involving hole-injection/hole-blocking materials that showed good current and power efficiencies. To understand the underlying mechanisms involved in the application of these molecules as emitters and transporters, a detailed photophysical characterization of molecules 4–6 was carried out. The absorption, steady-state fluorescence, phosphorescence, fluorescence lifetime, and phosphorescence lifetime measurements were carried out. The high quantum yield and efficient reverse intersystem crossing leading to delayed fluorescence emission makes the molecule a good emitter, and the charge delocalization properties leading to excimer formation make them efficient electron transporte...

Excimer laser lamellar keratoplasty of augmented thickness for keratoconus.

Abstract: Purpose We describe a modified surgical technique for the treatment of patients in the early stage of keratoconus, when it is still possible to correct the astigmatic ametropia with contact lenses. Methods Excimer laser lamellar keratoplasty of augmented thickness (ELLKAT) is a procedure in which a deep plano excimer laser ablation is done on the host cornea and a donor lamellar button--with or without an excimer laser refractive ablation on the posterior surface--is sutured into the recipient bed. In 12 of 20 eyes, the homoplastic button, which had parallel faces and was devoid of any dioptric power, was treated refractively on its stromal face with a Chiron Keracor 116 excimer laser to correct the axial and/or induced myopia present due to the weakened cornea. Results The 8 eyes that received donor buttons without excimer laser ablation had improved spectacle-corrected visual acuity from a mean preoperative value of 20/100 (no eye saw 20/40 or better before surgery) to a mean postoperative value of 20/30 after 18 months. Mean refractive astigmatism was reduced from 4.84 +/- 2.34 D to 1.00 +/- 0.46 D. Mean keratometric power was reduced from 56.75 +/- 8.01 D to 44.21 +/- 2.12 D. The associated mean spherical equivalent refraction was reduced from -4.75 to -3.00 D. Mean corneal thickness increased from 422.25 +/- 83 microns preoperatively to 562.87 +/- 57.81 microns postoperatively. The 12 eyes that received donor lamellar buttons treated with excimer laser also had improved spectacle-corrected visual acuity from a mean preoperative value of 20/100 to a mean postoperative value of 20/30 after 18 months. Astigmatism was reduced from a mean 4.84 +/- 2.77 D to 1.66 +/- 1.30 D; mean keratometric power was reduced from 56.08 +/- 7.00 D to 45.31 +/- 2.08 D; and the associated mean spherical equivalent refraction was reduced from -8.75 to -1.75 D. Corneal thickness increased from a mean 414.25 +/- 64.75 microns preoperatively to 576.75 +/- 28.23 microns postoperatively. Conclusion Compared to penetrating keratoplasty, excimer laser lamellar keratoplasty of augmented thickness for keratoconus has the advantage of preserving the host endothelium and of reducing the refractive error in keratoconus.