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Topic: Rovibronic excitation

In the News (Tue 17 Oct 17)

  MLF high resolution UV spectroscopy
The rotationally resolved excitation spectrum of the 0-0 band of the S1 <-- S0 transition in 2H-benzotriazole, at 286.4 nm, is obtained by using laser induced fluorescence spectroscopy in a molecular beam.
The A and B band transitions arise from excitations to respectively the zero and first overtone levels in the double-minimum potential of this out-of-plane vibration, which shows similarities to the so-called butterfly mode observed in other benzene derivatives.
The rotationally resolved fluorescence excitation spectrum of the 0-0 band in the S1 <-- S0 transition of 4-aminobenzonitrile (ABN) was recorded, at 299 nm, by using laser induced fluorescence in a molecular beam apparatus.
www.rijnh.nl /users/berden/uvhigh.html   (3351 words)

 Dr. David H. Mordaunt - List of Publications
Although the kinetic energy distributions resulting from excitation to the X 3Pi and c 1Pi states are clearly non-statistical, consideration of the potential energy surfaces indicates that dissociation from both states occurs via radiationless transitions to the X 3Sigma- state.
At excitation energies close to the origin, the excited, spin-forbidden CH(a 4Sigma-) + CO channel dominates, while the ground state CH(X 2Pi) + CO channel is the major channel at higher photon ene rgies.
Inspection of the poorly resolved structure evdient near the peak of the H atom kinetic energy distribution suggests the presence of substantial bending excitation and a-axis rotational excitation in the PH partner fragment.
bromine.cchem.berkeley.edu /david/abstracts.html   (5541 words)

 Conformational Structures of 3-Phenyl-1-propionic Acid, Its p-Hydroxy Derivative, and Its Hydrated Clusters   (Site not responding. Last check: 2007-10-23)
Analysis of the rovibronic band contours of these features is consistent with two conformational structures, referred to as anti and gauche.
Rovibronic band contour analysis of the 1:1 water complex of PPA yields a structure consistent with the acid acting as a proton donor.
The rotational band contour of the 1:2 water complex is consistent with a cyclic structure in which each water is involved in two hydrogen bonds.
pubs.acs.org /cgi-bin/abstract.cgi/jpcafh/1997/101/i04/abs/jp961913b.html   (274 words)

 [No title]   (Site not responding. Last check: 2007-10-23)
Unfortunately, the C-H stretch is weakly Franck-Condon active and hence its energy levels are difficult to access via SEP. Instead, infrared excitation detected by fluorescence depletion spectroscopy is used to populate the C-H rovibrational energy levels in the ground electronic state.
In this double resonance spectroscopy, first an IR laser (Optical Parametric Oscillator (OPO)) pulse passes through the jet and then a uv excitation laser is focussed along the same path.
Currently, work is in progress to record and analyze states throughout the fundamental and overtone regions for CH stretching.
molspect.mps.ohio-state.edu /frs/Abstracts/p016.html   (230 words)

 Rovibronic Spectroscopy of the Ethoxy Radical in a Supersonic Jet Environment   (Site not responding. Last check: 2007-10-23)
Rovibronic Spectroscopy of the Ethoxy Radical in a Supersonic Jet Environment
A frequency-doubled Nd:YAG-pumped dye laser with a nominal linewidth of 0.07 cm ^-1 served as the probe beam for excitation of the radical.
Extensive laser excitation spectra of jet-cooled C_2H_5O have been recorded in the 310-350 nm region with 0.15 cm ^-1 resolution.
flux.aps.org /meetings/BAPSAPR95/abs/SI1101.html   (188 words)

 Rovibronic coupling - Wikipedia, the free encyclopedia
Rovibronic coupling denotes the simultaneous interactions between rotational, vibrational, and electronic degrees of freedom in a molecule.
When a rovibronic transition occurs, the rotational, vibrational, and electronic states change simultaneously.
This page was last modified 11:31, 19 May 2006.
en.wikipedia.org /wiki/Rovibronic_excitation   (62 words)

 Tamar Seideman: Abstracts   (Site not responding. Last check: 2007-10-23)
The photofragment angular distributions following excitation of magnetic-rovibronic state-selected parent molecules depend sensitively on the photon frequency.
The results are traced to the complex excitation dynamics, which prepares a frequency-dependent superposition of rotational states, and to the strong forces exerted on the dissociating system in the region of the conical intersection.
By contrast,trajectories originating at off planar configurations sample a large portion of the excited surface before crossing to the lower diabate, resulting in high levels of internal excitation.
www.chem.northwestern.edu /~seideman/Publications/NH3.htm   (278 words)

 Welcome to Adobe GoLive 6
The collisions occur on a single excited-state potential surface; population is transferred from the ground electronic state to a single rovibronic level by means of a single-frequency dye or diode laser.
The ensuing emission is dispersed, and the intensities of the resulting spectral lines are used as measures of the excited-state population densities.
Hence there is no rotational excitation to remove energy from the collision and "quench" the vibrational excitation.
bstewart.web.wesleyan.edu /stewartresearch.html   (533 words)

 RESEARCH|zone Elliot R. Bernstein - Future Projects
The most important goal of these studies is to generate a reaction path (or coordinate) and potential energy surface for the radical reactions of atmospheric and combustion related chemistry.
This goal will be achieved through a two pronged approach: experimental studies of the reactions at different vibronic or rovibronic levels of the reactant complex and possible product state identification if other radical or optically accessible species are generated; and an extensive theoretical effort to calculate the observed reaction surfaces, coordinates, and product state distributions.
The ground state complex is not reactive because of a reaction barrier on this potential energy surface.
franklin.chm.colostate.edu /erb/home08.htm   (260 words)

 522-526   (Site not responding. Last check: 2007-10-23)
A method of fluorescence-decay measurement of sub-nanosecond time-resolution is presented which employs a narrow band pulsed dye laser for molecular excitation and a computer-controlled waveform digitizer for decay-data recording.
The kinematical parameters of single rovibronic molecular relaxation are thereby deduced routinely from the observed time-evolution of fluorescence decay through a curve-fitting procedure of convolution-integral treatment.
The method was applied to a systematic single rovibronic observation of fluorescence from the predissociative state of interhalogen molecule.
jjap.ipap.jp /link?JJAP/22/522   (211 words)

 <FSpano_research>   (Site not responding. Last check: 2007-10-23)
Optical excitations in polymers and polymer films is a robust field, with progress and advances fueled by the promising commercial applications of polymer-based or plastic optical devices such as organic light-emitting diodes.
We also developed and demonstrated a three laser excitation scheme to selectively excite a target mJ level within a rovibronic level of a diatomic molecule [9].
The theory is based on equations of motion which describe how the multilevel molecular density matrix evolves under the influence of two or more laser fields.
www.temple.edu /chemistry/main/faculty/Spano/FSpano_research.asp   (643 words)

 Vaccaro Lab - Veritas ex Lux at Yale University   (Site not responding. Last check: 2007-10-23)
Of particular interest are the structure and dynamics of polyatomic reagents that contain chemically-significant quantities of internal (rovibronic) energy.
Spectroscopic interrogation of these species provides detailed information on molecular topography, chemical bonding, and intramolecular dynamics in regimes of excitation akin to those encountered during a chemical reaction.
Starting with theoretically tractable triatomic and tetratomic systems, these studies explore the breakdown of small-amplitude, adiabatic approximations (e.g., normal modes and rovibronic separability) utilized for the canonical description of molecules near the bottom of their potential wells.
www.chem.yale.edu /~vaccaro/res.html   (318 words)

 [ information-center.be | Microwave_spectroscopy Resources ]   (Site not responding. Last check: 2007-10-23)
Rotational spectrum from a molecule (to first order) requires that the molecule have a dipole moment, that is a difference between the center of charge and the center of mass, or equivalently a separation between two unlike charges.
It is this dipole moment that enables the electric field of the light (microwave) to exert a torque on the molecule causing it to rotate more quickly (in excitation) or slowly (in de-excitation).
However, electronic excitation can lead to asymmetric charge distribution and thus providing a net dipole moment to the molecule.
information-center.be /Microwave_spectroscopy.html   (1812 words)

 AG Döbele - Gaseous Electronics Conference 2004   (Site not responding. Last check: 2007-10-23)
A combined inductive and capacitive frequency excitation can be used to obtain both a high plasma density and high-energy electrons.
Our aim is to control the electron energy distribution function of the plasma in such a way that the rovibronic states of the hydrogen and deuterium molecules in the electronic ground state are over-thermally populated.
Dissociative attachment of low-energy electrons to rovibronic highly excited molecules leads to the desired negative ions.
www.ilp.physik.uni-essen.de /doebele/tagungen/gec2003/gec2003.html   (443 words)

 Untitled Document
Laser light of a very small spectral band width is used in order to selectively excite desorbing molecules in the gas phase within a particular rovibronic state.
Changing the time between desorption and detection with keeping the wavelength of the detection laser constant results in time of flight spectra of a single rovibronic state.
The population of the rovibronic states at a given desorption velocity is obtained by a variation of the wavelength of the detection laser with a fixed time delay between desorption and detection.
www.chemie.uni-oldenburg.de /pc/al-shamery/quantum.html   (197 words)

The ability to align or orient molecular species prior to reaction is one of the main goals in the field of chemical reaction dynamics.
Such a mixed state can be used as a stepping stone for two-laser excitation of high energy triplet states.
Currently, the theory is being expanded to include nonperturbative excitation sequences and sequences using adiabatic following in order to maximize population in the target state.
astro.temple.edu /~spano   (710 words)

 Tamar Seideman: Abstracts
In particular we find that such cross-sections provide a mapping of the transition dipole vector which couples the ground state with the excited manifold.
This feature is traced to the coherent excitation of a small subset of helicity states in the absorption process.
It is suggested that the information contained in these angular distributions can be appreciated and extracted by preceding the experimental measurements with theoretical analysis.
www.chem.northwestern.edu /~seideman/Publications/mres.htm   (183 words)

 YCLS - ZEKE Excitation   (Site not responding. Last check: 2007-10-23)
This is due to dynamic state selection of intermediate rovibronic levels by the scan laser - resulting in the ionizing transition only probing a small subset of the available rotational manifold of the cation - rather than the static state selection of ZEKE-PFI.
Static state selection results in all available rovibronic transitions to the cation from the roatational levels encapsulated by the bandwidth of the pump laser contributing to the ZEKE-PFI signal, thus a much broader and generally (rotationally) unresolved peak.
The object, as implied above, is to gain information as to the structure of the cation, for which a program based on the spectator model [1] [2] of the ZEKE electron is used to simulate observed spectra by fitting to cationic rotational constants.
www.york.ac.uk /res/ycls/expt/zeke_ex.shtml   (422 words)

 Vibronic Relaxation among the Clements Bands of SO2 from the E-Band Excitation   (Site not responding. Last check: 2007-10-23)
Following the fast decay of the laser excited level, weak emissions from Clements A-F bands appeared almost simultaneously.
The simultaneous appearance of many Clements bands was attributed to fast rovibronic relaxation of the laser excited molecules among the dark levels.
Based on the wavelength dependence of the decay rates, the apparent continuum emissions were ascribed to the emissions from the rovibronically dispersed hybrid bright states and the low-lying rovibrational levels of the Ã
pubs.acs.org /cgi-bin/abstract.cgi/jpcafh/1999/103/i37/abs/jp990390f.html   (221 words)

 Mesosphere and Lower Thermosphere: Energetics and Dynamics Posters - SPA-Aeronomy [SA]
They are tentatively identified as rovibronic transitions involving high rotational quantum numbers from the (12,1) band of the b-X, the (8,1) band of the b'-X, and the (3,1) band of the o3-X transitions.
Integral cross sections for electron impact excitation out of the ground state (X $^{1}σ_{g}$$^ {+}$) to the A 3σ_{u}$$^{+}$, B 3$\Pi$$_{g}$, W 3Δ_{u}$, B$^\prime$ $^{3} σ_{u}$$^{-}$, a$^\prime$ $^{1}σ_{u}$$^{-}$, a $^{1}$$\Pi$$_{g}$, w $^{1}Δ_ {u}$, and C 3$\Pi$$_{u}$ states in N2 are reported at incident energies ranging between 10 and 100 eV.
The detector platform enabled the LBH emissions to be observed, using the UVIS engineering flight spare, at multiple radial positions relative to the electron beam axis, which was used to map the glow resulting from electron impact excitation of an optically thin swarm of N2 gas.
www.agu.org /meetings/fm05/fm05-sessions/fm05_SA11A.html   (4293 words)

 Rovibronic excitation   (Site not responding. Last check: 2007-10-23)
It is longer that the first edition but still focus...
A gem of scientific literature, Elementary Excitations in Solids is organized, well thought out, and readable.
Quasiparticle and Phonon Excitations in Nuclei : In Memory of Professor Vadim Soloviev (1925-1998)
www.freeglossary.com /Rovibronic_excitation   (190 words)

 Frequency measurements of hyperfine splittings in ground rovibronic states of I2 by stimulated resonant Raman ...   (Site not responding. Last check: 2007-10-23)
Frequency measurements of hyperfine splittings in ground rovibronic states of I2 by stimulated resonant Raman spectroscopy
An argon laser emitting at 514.5 nm, drives the coherence between hyperfine levels of the J''=13 or J''=15 rotational levels of the ground vibronic state, via resonant excitation of the hyperfine transitions of the optical resonances (43-0) P(13) or R(15).
We study the influence of the various experimental parameters on the line shape: the beam geometry, the laser modulation spectrum, the laser power, the molecular frequency shifts.
www.edpsciences.org /articles/epjd/abs/1999/04/d8236/d8236.html   (303 words)

 Applied Spectroscopy February 2000 Abstracts
The relative merits of five laser excitation schemes have been evaluated for photoionization spectrometry (PIS) measurements of NO in air.
All five schemes utilize wavelengths near 215 nm, which correspond to excitation of rovibronic transitions in the A
Excitation spectra of the five PIS schemes reveal a significant enhancement when 355 nm radiation is used for photoionization.
www.s-a-s.org /journal/00/feb2000_ea2.htm   (5240 words)

 JCE 2005 (82) 145 [Jan] Bond Length Dependence on Quantum States as Shown by Spectroscopy
This article discusses how linear-molecule rotational band spacings in infrared spectroscopy can be used as a qualitative, visual demonstration of the elongation of average bond lengths on vibrational excitation.
The method is based on a spreadsheet simulation of the vibration–rotation or rovibronic (electronic–vibration–rotation) spectrum and is applied to hydrogen chloride IR, iodine UV–vis, and nitrogen UV–vis spectra in this article.
The spreadsheet, description of the spreadsheet simulation, student notes, and an example of possible usage in an undergraduate laboratory exercise are available.
jchemed.chem.wisc.edu /Journal/Issues/2005/Jan/abs145.html   (296 words)

 NIST Quantum Physics Division 1999 - Technical Highlights   (Site not responding. Last check: 2007-10-23)
A 100 to 200 fs pulse from a Ti:sapphire regenerative amplifier prepares the coherent superposition of states from among eight rovibronic levels in the E electronic state.
A second, time-delayed, ultrafast pulse ionizes the molecules at a specific localization of the wave packet (internuclear separation and rotational angle).
This effect is dominated by excitation of the attractive, nonradiating molecular state, which gains a dipole moment at large atomic separation due to radiation retardation.
physics.nist.gov /TechAct.99/Div848/div848h.html   (2770 words)

 IngentaConnect Double resonance spectroscopy of several highly excited rovibroni...   (Site not responding. Last check: 2007-10-23)
The states were probed by excitation from the double-well E, F
states leading to perturbations that are predicted to vary considerably as a function of rotational and vibrational excitation.
Term energies for two rovibronic levels are reported for the first time.
www.ingentaconnect.com /content/iop/jphysb/2005/00000038/00000007/art00019   (222 words)

 Nuclear quadrupole hyperfine quantum beats in HCl and pyrimidine measured by the pump-probe method using REMPI/LIF ...   (Site not responding. Last check: 2007-10-23)
The pump-probe technique was applied and the experimental set up was optimized to achieve highest spectral resolution.
Following excitation of the HCl fundamental vibrational transition by a nanosecond IR laser pulse, the nuclear quadrupole coupling constants were determined to be
was excited and the quadrupole tensor elements for the rovibronic states
www.edpsciences.org /articles/epjd/abs/2000/03/d9211/d9211.html   (247 words)

 Selected Research Topics of the Modern Optics group
In an experiment on molecular HI (hydrogen iodide) using one- and three-photon excitation a final state was excited that is metastable with respect to both ionization and dissociation.
Surprisingly, it was found that the ionization and dissociation yields oscillate out-of-phase, if the relative phase between the one- and the three-photon field is varied.
Since the experiments use molecular tritium instead of atomic one, the so-called molecular final-state distribution (the probability that a certain amount of the nuclear decay energy leads to a rovibronic excitation of the generated daughter molecule
amo.physik.hu-berlin.de /research.html   (1694 words)

 Zeimen Wilfried Home Page   (Site not responding. Last check: 2007-10-23)
Rovibronic states from coupled diabatic potential energy surfaces
Singlet-triplet excitation spectrum of the CO-He complex I: Potential surfaces and bound-bound CO (a3PX1S+) transitions.
Singlet-triplet excitation spectrum of the CO-He complex II: Photodissociation and bound-free CO (a3PX1S+) transitions.
www.theochem.ru.nl /~zeimen   (144 words)

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