Photon absorption: classical treatment of nuclear motion

1982 ◽  
Vol 86 (18) ◽  
pp. 3615-3620 ◽  
Author(s):  
Jack Simons
Keyword(s):  
Photon Absorption ◽  
Nuclear Motion

scholarly journals The Photodissociation of Interstellar CH+

1980 ◽  
Vol 87 ◽  
pp. 283-286
Author(s):  
K. Kirby
Keyword(s):  
Interstellar Medium ◽  
Excited States ◽  
Cross Sections ◽  
Ground State ◽  
Theoretical Calculations ◽  
Dipole Transition ◽  
Photon Absorption ◽  
Nuclear Motion ◽  
Radiation Fields ◽  
Destruction Mechanism

Three new excited states of CH+ which can be reached by a dipole transition from the ground state with photon energies less than 13.6 eV have been obtained from accurate theoretical calculations. As these states are unbound with respect to nuclear motion, photon absorption into them results in dissociation of the molecule. Photodissociation cross sections have been calculated, and the CH+ photodissociation rates in the interstellar radiation field as a function of optical depth have been determined. The rates are approximately 500 times larger than previously assumed. We have compared these new photodissociation rates with the rates of other CH+ destruction mechanisms in three different models of the interstellar medium. Photodissociation appears to be a significant destruction mechanism in any model requiring large interstellar radiation fields.

scholarly journals Studies of 1fs scale dynamics in atoms and molecules

2014 ◽  
Author(s):  
Paolo Antonio Carpeggiani
Keyword(s):  
Time Scale ◽  
Extreme Ultraviolet ◽  
Energy Content ◽  
High Energy ◽  
Photon Absorption ◽  
Nuclear Motion ◽  
Barium Borate ◽  
Time Resolved ◽  
Linear Interaction ◽  
Molecular Potential

Coherent light pulses of few to hundreds of femtoseconds (fs) duration haveprolically served the eld of ultrafast phenomena. While fs pulses addressmainly dynamics of nuclear motion in molecules or lattice in the gas, liquidor condensed matter phase, the advent of attosecond (asec) pulses has inrecent years provided direct experimental access to ultrafast electron dynamics.However, there are processes involving nuclear motion in molecules andin particular coupled electronic and nuclear motion that occur in the few fsor even sub-fs time scale. Electronic excitations in molecules are commonlyin the VUV/XUV spectral region. Until recently most of the XUV sourceswere lacking either sucient pulse energy ( High Order Harmonic Generation(HOHG) sources) or ultrashort pulse duration (free electron lasers (FEL) [1]),thus preventing access to XUV-pump-XUV-probe measurements in the 1fsor asec temporal scale. In this work, by loose focusing a multi-cycle, highpower, fs Infra-Red (IR) laser (35fs, 160mJ=pulse, 805nm) into a Xenongas jet, the non-linear interaction results in frequency up-conversion and,under proper experimental conditions for Phase Matching (PM), in the formationof Attosecond Pulse Trains (APT). The application of InterferometricPolarization Gating (IPG) [88, 89] to this scheme allows the generation ofenergetic, broadband, coherent extreme-ultraviolet (XUV) continuum radiation.Although the temporal properties of the XUV pulse are aected by thelack of Carrier-Envelope Phase (CEP) stabilization [86], the XUV intensityis high enough to induce XUV multi-photon absorption in atomic [75] ormolecular system.So far, experimental eorts on this time scale have been restricted to XUVIRpump-probe schemes [34, 37, 41, 44, 73, 94], or in-situ electron-ion collisionmethods [59]. As the IR eld induced potential may distort the molecular potential[33], the use of IR-free technique to investigate the intrinsic moleculardynamics is of central importance.The present work focuses on the developmentof techniques for the investigation of such dynamics utilizing solelyXUV radiation and demonstrates proof of principle time resolved and XUVpump - XUV probe experiments, tracking ultrafast molecular dynamics.In order to induce the aforementioned XUV multi-photon processes, highXUV photon ux is required. In order to increase the XUV intensity, thesetup was upgraded to allow the use of 3m or 6m lenses for loose focus con-guration [36], and of a Barium Borate (BBO) crystal, for 2-color drivenHOHG [9, 14, 19, 25, 40, 95]. Although in our case the XUV intensity doesnot benet from the 2-color generation scheme, there is the possibility in theHOHG process to control the electron re-collision trajectories by acting on the parameters of the two laser elds [10]. With this option, the use of longtrajectories is convenient due to their higher energy content. The temporalcharacterization of the HOH obtained by the long trajectories in a 2-colordriving eld is an unexplored eld of investigation. We succeeded in thistask, recording 2nd order Interferometric Volume Auto Correlation [84, 85]traces by using, for the rst time, a multiply ionized atom [8, 87] as a nonlineardetector. The results show clearly the existence of a structure on the1fs scale.Exploiting the short duration of the above mentioned high energy pulses, allthe optically allowed excited states of H2 are coherently populated. Monitoringthe pump-probe delay dependent yield of protons, nuclear and electronic1fs scale dynamics are subsequently investigated and compared to the resultsof ab initio calculations. The revealed dynamics reects the intrinsicmolecular behavior as the XUV probe pulse, despite its still high intensity,hardly distorts the molecular potential. It was further feasible to follow theopening of the dissociative ionization channel through the 2+g (2pu) state,due to the stretching of the molecule. This is visible as a build-up of non-zerokinetic energies proton signal during the rst fs of the delay time.Utilizing individual harmonics, single (5th+5th; 7th+7th harmonic) and twocolor(5th + 9th harmonic) time resolved spectroscopy has been performedin molecular Oxygen, aiming at settling existing discrepancies of previousexperiments [23, 64]. Finally an attempt in observing energy resolved directtwo photon atomic double ionization [43, 48] through energy resolved electronspectroscopy has identied necessary actions and improvements for asuccessful implementation of such an experiment.

Second order interference in two photon absorption

1996 ◽  
Vol 43 (9) ◽  
pp. 1765-1771 ◽  
Author(s):  
M. W. HAMILTON and D. S. ELLIOTT
Keyword(s):  
Second Order ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon

Ruthenium Complexes for 1- and 2-Photon Photodynamic Therapy: From In Silico Prediction to In Vivo Applications

2020 ◽  
Author(s):  
Johannes Karges ◽  
Shi Kuang ◽  
Federica Maschietto ◽  
Olivier Blacque ◽  
Ilaria Ciofini ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
In Silico ◽  
Aqueous Solubility ◽  
The Body ◽  
Photon Absorption ◽  
Multicellular Tumor Spheroids ◽  
Spectral Window ◽  
Photon Excitation ◽  
Polypyridine Complexes

<div>The use of photodynamic therapy (PDT) against cancer has received increasing attention overthe recent years. However, the application of the currently approved photosensitizers (PSs) is somehow limited by their poor aqueous solubility, aggregation, photobleaching and slow clearance from the body. To overcome these limitations, there is a need for the development of new classes of PSs with ruthenium(II) polypyridine complexes currently gaining momentum. However, these compounds generally lack significant absorption in the biological spectral window, limiting their application to treat deep-seated or large tumors. To overcome this drawback, ruthenium(II) polypyridine complexes designed in silico with (E,E’)-4,4´-bisstyryl 2,2´-bipyridine ligands showed impressive 1- and 2-Photon absorption up to a magnitude higher than the ones published so far. While non-toxic in the dark, these compounds were found phototoxic in various 2D monolayer cells, 3D multicellular tumor spheroids and be able to eradicate a multiresistant tumor inside a mouse model upon clinically relevant 1-Photon and 2 Photon excitation.</div>

Studies of Two Photon Absorption in Heavy Metal Oxide Based Glasses

2010 ◽  
Vol 25 (3) ◽  
pp. 289-292 ◽  
Author(s):  
Fei-Fei CHEN ◽  
Tie-Feng XU ◽  
Shi-Xun DAI ◽  
Qiu-Hua NIE ◽  
Xiang SHEN ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Metal Oxide ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon
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