Introduction to Laser Spectroscopy

This book is intended to be used by students of chemistry, chemical engineering, biophysics, biology, materials science, electrical, mechanical, and other engineering fields, and physics. It assumes that the reader has some familiarity with the basic concepts of molecular spectroscopy and quantum theory, e.g., the concept of the uncertainty principle, quantized energy levels, but starts with the most basic concepts of laser physics and develops the advanced topics of modern laser spectroscopy including femtochemistry. The major distinction between this book and the many fine books available on laser physics and time resolved spectroscopy is its emphasis on a general approach that does not focus mainly on an extensive consideration of time resolved spectroscopy. Books at the correct level of presentation for beginners tend to be focused either totally or mainly on the basic fundamentals of lasers and include only a minimal amount of material on modern ultrashort laser spectroscopy and its chemical, physical and biological applications. On the other hand, books that contain the desired material to a significant degree, are too advanced, requiring too much prior knowledge of nonlinear optics, quantum theory, generation of ultrafast pulses, detection methods, and vibrational and electronic dynamics. This book is intended to fill the gap. More advanced problems of modern ultrafast spectroscopy are developed in the later chapters using concepts and methods from earlier chapters [...]

Ultrafast Dynamics of Metal Complexes of Tetrasulfonated Phthalocyanines at Biological Interfaces: Comparison between Photochemistry in Solutions, Films, and Noncancerous and Cancerous Human Breast Tissues

International audienceA promising material in medicine, electronics, opto-electronics, electrochemistry, catalysis, and photophysics, Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) is investigated at biological interfaces of human breast tissue by means of steady-state and time-resolved pump?probe spectroscopies: IR, Raman, UV?vis, fluorescence, and electronic transient absorption by pump?probe spectroscopy. Spectrally resolved pump?probe data were recorded on time scales ranging from femtoseconds to nanoseconds and give insight into molecular interactions and primary events in the interfacial region. The nature of these fast processes and pathways of the competing relaxation processes from the initially excited electronic states in AlPcS4 films and at biological interfaces of human breast cancerous and noncancerous tissues is studied. Comparison between photochemical dynamics in the biological environment of the human breast tissues and that occurring in aqueous solutions is presented. The excited-state absorption (ESA) decays and bleaching recovery of the ground state have been fitted in the time window extending to nanoseconds (0?1 ns). We found that the excited-state dynamics of AlPcS4 at biological interfaces of human breast tissue is extremely sensitive to the biological environment and differs drastically from that observed in solutions and films. We demonstrated that the ultrafast dynamics at biological interfaces is described by three time constants in the ranges of 110?170 fs, 1?7 ps, and 20?60 ps. We were able to ascribe these three time constants to the primary events occurring in phthalocyanine at biological interfaces. The shortest time constants have been assigned to vibrational wavepacket dynamics in the Franck?Condon region down to the local minimum of the excited-state S1. The 1?7 ps components have been assigned to vibrational relaxation in the excited and ground electronic states. In contrast to the dynamics observed in aqueous solutions with the components in the range of 150?500 ps assigned to decay from S1 to the ground electronic state, these slow components have not been recorded in human breast tissue. We have shown that the lifetimes characterizing the first excited-state S1 in the interfacial regions of the breast tissue are markedly shorter than those in solution. It suggests that molecular structures responsible for harvesting of the light energy in biological tissue find their own ways for recovery through some special features of the potential energy surfaces such as conical intersections, which facilitate the rate of radiationless transitions. We found that the dynamics of photosensitizers in normal (noncancerous) breast tissue is markedly faster than that in cancerous tissue

Ultrafast Dynamics of Metal Complexes of Tetrasulphonated Phthalocyanines

International audienceA promising material in medicine, electronics, optoelectronics, electrochemistry, catalysis, and photophysics, tetrasulphonated aluminum phthalocyanine (AlPcS4), is investigated by means of steady-state and time-resolved pump?probe spectroscopies. Absorption and steady-state fluorescence spectroscopy indicate that AlPcS4 is essentially monomeric. Spectrally resolved pump-probe data are recorded on time scales ranging from femtoseconds to nanoseconds. The nature of these fast processes and pathways of the competing relaxation processes from the initially excited electronic states in aqueous and organic (dimethyl sulfoxide) solutions are discussed. The decays and bleaching recovery have been fitted in the ultrafast window (0-10 ps) and later time window extending to nanoseconds (0-1 ns). While the excited-state dynamics have been found to be sensitive to the solvent environment, we were able to show that the fast dynamics is described by three time constants in the ranges of 115-500 fs, 2-25 ps, and 150-500 ps. We were able to ascribe these three time constants to different processes. The shortest time constants have been assigned to vibrational wavepacket dynamics. The few picosecond components have been assigned to vibrational relaxation in the excited electronic states. Finally, the 150-500 ps components represent the decay from S1 to the ground state. The experimental and theoretical treatment proposed in this paper provides a basis for a substantial revision of the commonly accepted interpretation of the Soret transition (B transition) that exists in the literature

Raman imaging at biological interfaces: applications in breast cancer diagnosis

Abstract Background One of the most important areas of Raman medical diagnostics is identification and characterization of cancerous and noncancerous tissues. The methods based on Raman scattering has shown significant potential for probing human breast tissue to provide valuable information for early diagnosis of breast cancer. A vibrational fingerprint from the biological tissue provides information which can be used to identify, characterize and discriminate structures in breast tissue, both in the normal and cancerous environment. Results The paper reviews recent progress in understanding structure and interactions at biological interfaces of the human tissue by using confocal Raman imaging and IR spectroscopy. The important differences between the noncancerous and cancerous human breast tissues were found in regions characteristic for vibrations of carotenoids, fatty acids, proteins, and interfacial water. Particular attention was paid to the role played by unsaturated fatty acids and their derivatives as well as carotenoids and interfacial water. Conclusions We demonstrate that Raman imaging has reached a clinically relevant level in regard to breast cancer diagnosis applications. The results presented in the paper may have serious implications on understanding mechanisms of interactions in living cells under realistically crowded conditions of biological tissue. </jats:sec

Introduction to laser spectroscopy

This book is intended to be used by students of chemistry, chemical engineering, biophysics, biology, materials science, electrical, mechanical, and other engineering fields, and physics. It assumes that the reader has some familiarity with the basic concepts of molecular spectroscopy and quantum theory, e.g., the concept of the uncertainty principle, quantized energy levels, but starts with the most basic concepts of laser physics and develops the advanced topics of modern laser spectroscopy including femtochemistry. The major distinction between this book and the many fine books available on laser physics and time resolved spectroscopy is its emphasis on a general approach that does not focus mainly on an extensive consideration of time resolved spectroscopy. Books at the correct level of presentation for beginners tend to be focused either totally or mainly on the basic fundamentals of lasers and include only a minimal amount of material on modern ultrashort laser spectroscopy and its chemical, physical and biological applications. On the other hand, books that contain the desired material to a significant degree, are too advanced, requiring too much prior knowledge of nonlinear optics, quantum theory, generation of ultrafast pulses, detection methods, and vibrational and electronic dynamics. This book is intended to fill the gap. More advanced problems of modern ultrafast spectroscopy are developed in the later chapters using concepts and methods from earlier chapters [...]