Wavelength-resolved Emission Research Articles

Wavelength- and Time-Resolved Investigation of Laser-Induced Plasmas as a Continuum Source

Time- and wavelength-resolved laser-induced plasma emission spectra in helium, argon, nitrogen, air, and helium/argon mixture were obtained from 200 to 700 nm. Stability studies showed that plasmas formed in helium had about 5% relative standard deviation in emission at most wavelength regions. A radiant intensity of 8 × 1011 photons/pulse sr was produced at 633 nm with a moderate laser power. Plasma temporal development was investigated in various gases. In general, the continuum emission was observed only during the first few microseconds following the laser onset. Plasmas in argon have the longest decay time, followed by helium and nitrogen. The feasibility of using the laser-induced plasma as a continuum source for the study of transient molecular absorption was demonstrated.

Glow-discharge optical spectroscopy as a diagnostic of sputtered permalloy film composition and saturation magnetostriction

We show that the composition and saturation magnetostriction of sputtered permalloy films can be correlated with the relative intensities of iron and nickel atomic emissions from a 13.56-MHz rf glow discharge. Wavelength-resolved emission spectra as a function of discharge pressure were recorded while sputtering iron and permalloy targets. Intensities of some emission lines were highly correlated, so that their ratios were nearly independent of argon pressure. This occurred in spite of a ∼50-fold change in the brightness of the glow over the pressure range studied, and suggested that the stoichiometry of the sputtering target and the sputtered permalloy film can each be assessed during the sputtering process. The selection of appropriate emission lines is discussed, along with considerations of the type of equilibrium distribution prevalent in a sputtering discharge. We used five sputtering targets with different Ni/Fe ratios to grow films. The films were analyzed in terms of composition, stress, and saturation magnetostriction. Film stress was not observed to vary significantly with sputtering target composition. A high degree of correlation was observed between Fe/Ni emission intensity ratio, target composition, film composition, and saturation magnetostriction.

An aberration-corrected time- and spatially-resolved spectrometer for studies of transient discharges

A time- and wavelength-resolved spectrometer system for triggered analytical sources is described. The optical arrangement is designed to permit (1)time-, space-, and wavelength-resolved emission, absorption, and fluorescence; (2) Schlieren; (3) interference; (4) interferometric/Schlieren; and (5J anomalous dispersion “hook” spectroscopies to be performed. Only minor adjustments are required in converting the instrument between experiments. The instrument is based on compensation of optical aberrations through use of an over-and-under and a side-by-side mirror pair to correct the astigmatism and coma of an asymmetric Czerny-Turner spectrograph. An intermediate slit located in an astigmatic image plane is used to select and isolate the observation region of the emission source. For emission experiments time resolution results from rotation of a six-facet optical polygon which sweeps an image of the selected observation window past the spectrograph entrance slit. All optical elements are mounted on a mechanically-rigid, referenceable, vibrational-isolated optical support system. Instrument performance is discussed.

Wavelength-Resolved Single-Spark Emission Images with the Use of a Charge Coupled Device Detector

With the use of charge coupled device observation technology, single spark data have shown a limitation of current sample introduction models for the high-voltage atmospheric pressure spark. Two-dimensional spatial images of wavelength-resolved data show that atomic emission varies not only in position but also in amplitude. Vapor jets are not observed, but rather nebulous clouds of emission, greatly varying in intensity, are seen.

Free jet-cooled laser-induced fluorescence spectrum of methoxy. 1. Vibronic analysis of the ~A and ~X states

The methoxy free radical has been formed in a supersonic free jet expansion by KrF photolysis of methyl nitrite. Its laser-induced fluorescence excitation and wavelength-resolved emission spectra have been recorded at low temperature. This paper reports the vibronic analysis of the CH/sub 3/O and CD/sub 3/O /tilde A//sup 2/A/sub 1/ /leftrightarrow/ /tilde X//sup 2/E electronic spectra. A new value for the electronic origin has been determined as well as a nearly complete set of vibrational frequencies.

ChemInform Abstract: LASER‐INITIATED CHLORINE/HYDROCARBON CHAIN REACTIONS: TIME‐RESOLVED INFRARED EMISSION SPECTRA OF PRODUCT VIBRATIONAL EXCITATION

Rapid gas-phase chain reactions of Cl/sub 2//hydrocarbon mixtures are initiated by selective laser photodissociation of Cl/sub 2/ and investigated by time-resolved infrared emission spectra of chain products. The basic two-center chain chlorination reaction sequence is Cl. + RH ..-->.. HCl(nu) + R., R. + Cl/sub 2/ ..-->.. RCl/sup + +/ + Cl. (rate constants k/sub 1/ and k/sub 2/ apply to the reaction sequence). At low hydrocarbon reagent pressures ((RH) less than or equal to 20 Pa), analysis of emission from HCl(nu) is used to determine the chain rate constants k/sub 1/ and k/sub 2/ under controlled room temperature conditions. At higher pressures of RH (greater than or equal to 300 Pa) the chain reaction generates vibrationally excited polyatomic products, RCl/sup + +/, at rates comparable to or faster than relaxation of RCl/sup + +/. Time- and wavelength-resolved emission from vibrationally hot RCl/sup + +/ is used to investigate chain reaction behavior in this regime of rapidly rising temperatures. Extensive vibrational emission from reagent molecules is also observed, indicating a rapid and complete sharing of product vibrational excitation with the reagent molecules. The dispersed emission spectra of the products (3.0 to 15.0 ..mu..m) is fit by a simple model thatmore » assumes a common vibrational temperature, T/sub vib/, and varies the relative concentrations of the emitters. Product isomer ratios obtained from these spectral fits are in good agreement with literature values. Vibrational temperatures as high as 700/sup 0/K are observed. These are significantly hotter than the measured bulk gas temperatures (400 to 500/sup 0/ K), which suggests that the vibrational and translational degrees of freedom are not in equilibrium under the rapid burning conditions in these systems.« less

Ne matrix spectra of the sym-C 6Br 3F 3+ radical cation

The electronic absorption and laser excited, wavelength resolved fluorescence spectra of the title cation have been observed in solid Ne matrix and vibrationally analysed. The vibrational structure of the excited B 2A 2 ″ state shows close similarity to the parent compound. The X 2E″ ground state structure is strongly perturbed and irregular owing to a large Jahn—Teller distortion. The data are analysed in terms of a recently developed, sophisticated multimode Jahn—Teller theoretical model. We have generated the sym-C 6Br 3F 3 + cations in solid Ne matrix and obtained their wavelength resolved emission and absorption spectra. T ground electronic X 2E″ state exhibits an irregular and strongly perturbed vibrational structure, which can be successfully modeled using sophisticated multimode Jahn—Teller theory.

ChemInform Abstract: SELECTIVELY EXCITED, WAVELENGTH RESOLVED EMISSION SPECTRA OF GASEOUS ORGANIC IONS

Chemischer InformationsdienstVolume 11, Issue 40 Physical Organic Chemistry ChemInform Abstract: SELECTIVELY EXCITED, WAVELENGTH RESOLVED EMISSION SPECTRA OF GASEOUS ORGANIC IONS T. SEARS, T. SEARSSearch for more papers by this authorT. A. MILLER, T. A. MILLERSearch for more papers by this authorV. E. BONDYBEY, V. E. BONDYBEYSearch for more papers by this author T. SEARS, T. SEARSSearch for more papers by this authorT. A. MILLER, T. A. MILLERSearch for more papers by this authorV. E. BONDYBEY, V. E. BONDYBEYSearch for more papers by this author First published: October 7, 1980 https://doi.org/10.1002/chin.198040048AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue40October 7, 1980 RelatedInformation

Selectively excited, wavelength resolved emission spectra of gaseous organic ions

Previously reported laser excitation spectra of a number of gaseous organic ions have characterized the vibrational structure of the excited electronic states, but have given only slight information about that structure in the ground electronic state. We now report wavelength resolved emission spectra induced by laser excitation of specific excited state vibrational levels for C6H3F3+ and C6H3Cl3+. These spectra directly characterize the ground state vibrational structure. Excitation of the vibrationless level confirms that previously reported ground state vibrational frequencies obtained for the ions in Ne matrices are characteristic of the isolated molecules. Similar spectra obtained by pumping excited, nontotally symmetric, vibrational levels show directly, for the first time, the split components of the most active Jahn–Teller modes in the ground electronic state. The splittings show that several previous analyses of Jahn–Teller effects in these ions were either incorrect or incomplete, and provide the necessary additional information to perform a complete analysis.

Laser-induced fluorescence spectra of several nonsymmetrical fluorobenzene radical cations in solid Ne

Laser-induced fluorescence excitation and wavelength-resolved emission spectra of the radical cations of 1,2,4,5-C 6H 4F 2, 1,2,3,4-C 6H 2F 4, 1,2,3,5-C 6H 2F 4, and C 6HF 5 have been observed in solid Ne. These spectra provide extensive information about the vibrational structure of both the excited and ground states of the cations. The results are found to be in excellent agreement with a recent gas phase laser-induced fluorescence experiment on these ions, but discrepancies are found with recent studies of their optical emission spectra from a discharge source.

Picosecond time-resolved energy transfer in Porphyridium cruentum. Part I. In the intact alga

The wavelength-resolved fluorescence emission kinetics of the accessory pigments and chlorophyll a in Porphyridium cruentum have been studied by picosecond laser spectroscopy. Direct excitation of the pigment B-phycoerythrin with a 530 nm, 6 ps pulse produced fluorescence emission from all of the pigments as a result of energy transfer between the pigments to the reaction centre of Photosystem II. The emission from B-phycoerythrin at 576 nm follows a nonexponential decay law with a mean fluorescence lifetime of 70 ps, whereas the fluorescence from R-phycocyanin (640 nm), allophycocyanin (660 nm) and chlorophyll a (685 nm) all appeared to follow an exponential decay law with lifetimes of 90 ps, 118 ps and 175 ps respectively. Upon closure of the Photosystem II reaction centres with 3-(3,4-dichlorophenyl)-1,1-dimethylurea and preillumination the chlorophyll a decay became non-exponential, having a long component with an apparent lifetime of 840 ps. The fluorescence from the latter three pigments all showed finite risetimes to the maximum emission intensity of 12 ps for R-phycocyanin, 24 ps for allophycocyanin and 50 ps for chlorophyll a. A kinetic analysis of these results indicates that energy transfer between the pigments is at least 99% efficient and is governed by an exp −At 1 2 transfer function. The apparent exponential behaviour of the fluorescence decay functions of the latter three pigments is shown to be a direct result of the energy transfer kinetics, as are the observed risetimes in the fluorescence emissions.

Rigid cage effect on ICl photodissociation and B O+ fluorescence in rare gas matrices

The relaxation dynamics of matrix isolated ICl have been studied via time and wavelength resolved emission. Vibrationally relaxed B O+ fluorescence occurs following irradiation both above and below the gas phase dissociation barrier. The fluorescence quantum yield is near unity independent of excitation wavelength, and I35Cl and I37Cl progressions clearly separate in the emission spectrum. The excitation spectrum shows discrete thresholds for v′ = 0−3 and only smooth structure above the dissociation barrier, indicating that constrictive cage forces cause no significant vibrational quantization in the B O+ repulsive region. Irradiation below the v′ = 0 threshold also yields B O+ fluorescence by a weak sequential two photon process. Vibrational line shapes show that excitation below the barrier produces relaxed phonon emission, while irradiation above the barrier produces unrelaxed phonon structure. It is proposed that unrelaxed emission occurs from metastable orientational (librational) local minima in the v′ = 0 B O+ state. The photodissociation−recombination sequence appears to be a general method for populating phonon states not Franck−Condon accessible in bound−bound absorption.

Radiative and radiationless transition phenomena in 1,4-, 1,3-, and 1,2-diazanaphthalene vapors

A pulsed, frequency doubled dye laser has been used to study time and wavelength resolved emission from low pressure quinoxaline, quinazoline, and cinnoline vapors. The S1, 1(n−π*) states of quinoxaline and quinazoline undergo statistical limit intersystem crossing, while the S2 (π−π*) states undergo S2−S1 and singlet-triplet intermediate strong coupling. Excitation into S2 yields a two-component ``fluorescence'' having an S1-type emission spectrum, and a longer component lifetime 102–103 longer than predicted by the S0−S2 f number. This anomalous emission is discussed principally in terms of a sequential decay theory of Tric and co-workers. Intermediate strong coupling appears to evolve into statistical limit coupling as a function of excitation energy. The 3B2 quinoxaline collision free phophorescence lifetime is within a factor of 2 of its value in condensed phases at low temperature. Thus the existance of rotational degrees of freedom in the gas does not significantly enhance the T1→S0 intersystem crossing rate, in disagreement with a recent theory. Cinnoline exhibits no detectable long-lived phosphorescence or intermediate strong coupling emission.

Time- and wavelength-resolved emission line profiles for pulsed Cu and Ag hollow cathode lamps

Time-resolved, line emission wavelength profiles were obtained for a copper and a silver pulsed hollow cathode lamp with the use of a piezoelectrically driven interferometer. A computer was used to control the timing of the sweep of the interferometer, the pulsing of the source, and the acquisition, averaging, sorting and display of data. Minor manipulation of the data stored in core facilitated the presentation of intensity vs wavelength emission profiles in a time-resolved form. Ten sequential line profiles spaced at 21 μsec time intervals were obtained. The copper hollow cathode lamp was driven at 100 Hz with pulse currents of up to 400 mA. Pulses lasted for up to 300 μsec. Line profiles changed dramatically during a pulse and showed extreme self-reversal of the resonance emission lines after 100 μsec. Variations of line profile with dc background current level and spatial position within the discharge were also investigated. Uncorrected line widths of each of the doublets of the Cu(I) 324.7 nm resonance line measured during the first 21 μsec of the discharge, where they were narrowest, ranged from 0.0012 to 0.0022 nm, including an instrumental broadening contribution estimated to be less than 0.0004 nm. The silver lamp showed extreme self-reversal even during the first 21 μsec.