Photochemistry with high power ultraviolet lasers

1983 ◽  
Vol 61 (5) ◽  
pp. 1023-1026 ◽  
Author(s):  
R. J. Donovan ◽  
C. Fotakis ◽  
A. Hopkirk ◽  
C. B. McKendrick ◽  
A. Torre
Keyword(s):  
Energy Distribution ◽  
High Power ◽  
Single Photon ◽  
Laser Induced Fluorescence ◽  
Multiphoton Excitation ◽  
Dissociation Process ◽  
Two Photon ◽  
Photon Excitation ◽  
Ultraviolet Lasers ◽  
Two Photon Excitation

Rotationally resolved photofragment fluorescence from OH(A2Σ+) following the coherent two-photon excitation of H2O with a KrF laser (248 nm), is reported and the dynamics of the dissociation process are discussed. Fluorescence from CN(B2Σ+) following two-photon excitation of ICN is also described. In both cases the energy distribution in the photofragments is shown to differ significantly from that observed with single-photon excitation at closely similar energies.Two further examples of multiphoton excitation, involving CS2 and SO2, are briefly discussed. In these cases absorption of a further photon, by fragments produced in the primary step, gives rise to strong laser-induced fluorescence.

Autofluorescence of epithelial tissue: single-photon versus two-photon excitation

2008 ◽  
Vol 13 (5) ◽  
pp. 054010 ◽  
Author(s):  
Wei Zheng ◽  
Yicong Wu ◽  
Dong Li ◽  
Jianan Y. Qu
Keyword(s):  
Single Photon ◽  
Epithelial Tissue ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

scholarly journals Cardiovascular Imaging Using Two-Photon Microscopy

2008 ◽  
Vol 14 (6) ◽  
pp. 492-506 ◽  
Author(s):  
John A. Scherschel ◽  
Michael Rubart
Keyword(s):  
Laser Scanning ◽  
Single Photon ◽  
Second Harmonic ◽  
Multiphoton Microscopy ◽  
Cardiovascular Imaging ◽  
Laser Scanning Microscopy ◽  
Dye Transfer ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

AbstractTwo-photon excitation microscopy has become the standard technique for high resolution deep tissue and intravital imaging. It provides intrinsic three-dimensional resolution in combination with increased penetration depth compared to single-photon confocal microscopy. This article will describe the basic physical principles of two-photon excitation and will review its multiple applications to cardiovascular imaging, including second harmonic generation and fluorescence laser scanning microscopy. In particular, the capability and limitations of multiphoton microscopy to assess functional heterogeneity on a cellular scale deep within intact, Langendorff-perfused hearts are demonstrated. It will also discuss the use of two-photon excitation-induced release of caged compounds for the study of intracellular calcium signaling and intercellular dye transfer.

scholarly journals Non-linear Simultaneous Two-Photon Excitation Energy Transfer in the Wrong Direction

1997 ◽  
Vol 17 (3) ◽  
pp. 161-174 ◽  
Author(s):  
M. Nickoleit ◽  
A. Uhl ◽  
J. Bendig
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Single Photon ◽  
Energy Levels ◽  
Excitation Energy Transfer ◽  
Laser Exposure ◽  
Two Photon ◽  
Photon Excitation ◽  
Covalently Linked ◽  
Two Photon Excitation

The simultaneous two-photon excitation energy transfer (SEET) was demonstrated for the first time using trichromophoric model compounds. Two identical donors (A–antenna) were covalently linked to an energy acceptor unit (T–target) with different energy levels preventing energy transfer of a single photon. At high intensity illumination (laser exposure) of a trichromophoric system A∼T∼A (A–fluorescein, erythrosin; T-Estilbene), sufficient to excite both of the appended donor subunits, population of the target excited state may occur via simultaneous energy transfer of two photons, one from each donor. In order to restrict reverse energy transfer from the higher energy target to the lower energy donor(s) it is necessary that the excited target unit undergoes an efficient photoreaction. In the investigated case this was achieved by photoisomerization of the stilbene unit used for monitoring of the SEET.

Multi-photon Fluorescence Micro-spectroscopy of Plant Tissues

2000 ◽  
Vol 6 (S2) ◽  
pp. 808-809
Author(s):  
F. J. Kao ◽  
B. L. Lin ◽  
P. C. Cheng
Keyword(s):  
Single Photon ◽  
Second Harmonic ◽  
Spectral Response ◽  
Broad Band ◽  
Small Contribution ◽  
Two Photon ◽  
Photon Excitation ◽  
Photon Spectra ◽  
Photon Fluorescence ◽  
Two Photon Excitation

Considering its non-linear nature, two-photon excitation may generate very different spectral response in samples when compared with single photon excitation. It is thus necessary to measure the two-photon spectra of samples, so that the two-photon fluorescence microscopic images can be properly interpreted. Fluorescence spectra obtained from bulk samples may not provide useful information for microscopy. For instance, due to the relatively small contribution to the total fluorescence intensity, a small number of fluorescent particles in a generally fluorescing specimen may escape detection when the spectrum of the specimen as a whole is obtained. Under two-photon excitation, the background noise can be greatly reduced due to the naturally limited excitation volume of focused laser beam. In addition, signals resulted from second harmonic generation (SHG) may be mixed with low level broad-band background autofluorescence which is commonly found in biological specimen. Therefore, measuring fluorescence spectrum from a micro-focused volume is essential for the proper interpretation of multi-photon fluorescence images.

Investigation of the luminescence properties of ZnO clusters induced by single-photon and two-photon excitation

2021 ◽  
Vol 18 (10) ◽  
pp. 106003
Author(s):  
Jun Dai ◽  
Zhengguo Li ◽  
Yi Zhang ◽  
Yongzhu Chen ◽  
Xing Zhu ◽  
...  
Keyword(s):  
Single Photon ◽  
Luminescence Properties ◽  
Two Photon ◽  
Photon Excitation ◽  
Zno Clusters ◽  
Two Photon Excitation

Limiting Factors on Image Quality in Imaging through Turbid Media under Single-photon and Two-photon Excitation

2000 ◽  
Vol 6 (2) ◽  
pp. 156-160 ◽  
Author(s):  
S. P. Schilders ◽  
M. Gu
Keyword(s):  
Multiple Scattering ◽  
Single Photon ◽  
Image Resolution ◽  
Turbid Medium ◽  
Turbid Media ◽  
Limiting Factors ◽  
Limiting Factor ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

The effect of multiple scattering in a turbid medium on single-photon and two-photon fluorescence microscopy is experimentally investigated for different scattering characteristics including scattering anisotrophy and optical thickness of a turbid medium. It is demonstrated that two-photon excitation can provide significant improvement in penetration depth through turbid media, due to reduced scattering experienced by the excitation beam. It is also shown that the limiting factor in obtaining high-quality images under singlephoton excitation is the fast degradation of image resolution caused by multiple scattering, while for twophoton excitation it is limited by the degradation of image contrast due to the reduction in fluorescence strength.

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