Dye Laser Spectrometer Research Articles

A Dye Laser Spectrometer Stabilized to a Hyperfine Component of Molecular Iodine for the Magnetooptical Trap of Sodium Atoms

A dye laser spectrometer, whose sideband frequency was stabilized to a hyperfine component of molecular iodine, was developed for the magnetooptical trap of sodium atoms. The frequency difference between the transition from 3S1/2, F=2 to the 3P3/2, F′=3 of a sodium atom and the f component of the P(38) line in the 15-2 band of the molecular iodine was measured to be 1047.2±0.3 MHz. The optimum laser frequency for the magnetooptical trap of a sodium atom was obtained.

Thermal stability of fullerenes: a shock tube study on the pyrolysis of and

The thermal stability of fullerenes and dispersed in Ar was studied behind shock waves by following the time-dependent absorption and emission of the proposed decomposition product . The gas - particle mixtures filled into the shock tube were heated to temperatures at pressures of . Because of the relatively high vapour pressure of the fullerenes, they evaporate in a few microseconds so that both and are in the gas phase during most of the observation time. concentration profiles were measured by a ring dye laser spectrometer at . Simultaneously, the time behaviour of spectrally resolved light emitted from the shock-heated aerosol was recorded by an intensified CCD camera. A simplified reaction mechanism with both formation and consumption reactions was proposed and the experimental results were discussed in terms of kinetic parameters. Rate coefficients and of the initial pyrolysis reactions (R1) and (R2) were determined. Two different models for the further decomposition of fullerene fragments were discussed and compared with computer simulations.

C2 formation during high-temperature pyrolysis of fullerene C60 in shock waves

The formation of C{sub 2} during thermal decomposition of fullerene C{sub 60} was studied behind shock waves by time dependent absorption and emission measurements. The experiments were performed in the temperature range 2450 {<=} T {<=} 3450 K at pressure in the range 1.1 {<=} p {<=} 2.0 bar. C{sub 2} concentration profiles were measured with a ring dye laser spectrometer at v = 21393.12 cm{sup -1}. Simultaneously, the time behavior of spectrally resolved light emitted from the shock-heated aerosol was recorded by an intensified CCD camera. A simplified reaction mechanism with both C{sub 2} formation and consumption reactions was proposed, and the experimental results were discussed in terms of kinetic parameters. A rate coefficient of the initial reaction C{sub 60} + Ar {yields} C{sub 2} + C{sub 58} + Ar, k{sub 1} = 2.7 x 10{sup 17} exp(-495 kJ/mol/RT) cm{sup 3} mol{sup -1} s{sup -1}, was determined. Two different models for the further decomposition of fullerene fragments were discussed and compared with computer simulations. 17 refs., 6 figs.

High-resolution spectroscopy with laser-cooled and trapped calcium atoms

We report on high-resolution spectroscopy with two different samples of calcium atoms, in a laser-cooled and deflected beam and in a magneto-optical trap. The atomic beam was excited by spatially separated laser fields. For spectroscopy with stored atoms in a magneto-optical trap we used a multiple-pulse excitation scheme. The resolution as low as 2.5 kHz was limited by residual frequency fluctuations of our dye-laser spectrometer. The results should allow to establish a frequency standard with a relative uncertainty below 10−14.

A dye laser spectrometer for high resolution spectroscopy

Abstract A high resolution dye laser spectrometer is described. The laser frequency is locked to a resonance frequency of a high finesse Fabry-Perot cavity by a sideband modulation technique. The residual frequency fluctuations of the stabilized laser were measured with respect to an independent frequency discriminator. From this measurement a value of the Allan variance of 10 -14 at sampling times ranging between 10 -5 and 1 s was derived, indicating a laser linewidth of 10 Hz. By Doppler-free two-photon excitation of rubidium Rydberg states we observed optical Ramsey fringes with a linewidth (fwhm) of 7.5 kHz limited by the time-of- flight of the atoms between the separated interaction zones.

On the reaction of CH with CO studied in high temperature CH4/Ar + CO mixtures

AbstractIn this study a ring dye laser spectrometer was employed for in‐situ measurements of CH concentrations in the reaction zone behind shock waves. The time dependent absorption in the Q‐branch of the A2Δ — X2Π band of CH at 431.1311 nm caused by the formation and consumption of CH radicals during the shock induced pyrolysis of a few ppm methane in argon was recorded. The CH concentration could directly be calculated from the measured absorption by applying the Lambert‐Beer law. By adding a few percent CO to the initial mixtures, the CH concentration profiles were significantly perturbed. Both the perturbed and unperturbed CH concentration profiles have been compared with those calculated from reaction kinetic simulations. A reaction mechanism describing the CH concentration history in the CH4/Ar and CH4/CO/Ar systems between 2900 K and 3500 K was developed. By a fitting procedure, a value of k1 = 1.85 × 1011 cm3 mol−1 s−1 was obtained for the most important perturbation reaction CH + CO → C2O + H.

The laser spectroscopy of highly excited vibrational states of HD 16O

The absorption spectra of HD 16O were recorded using a F 2 +:LiF color center intracavity laser spectrometer in the 0.9-μm region and an optoacoustic dye laser spectrometer in the 0.59-μm spectral region. Energy levels and rotational and centrifugal distortion constants of the (003) and (005) states were determined. Improved sets of vibrational and vibration-rotation constants have been obtained by fitting all available data for the energy levels of HDO.

Observation of the Stark effect in high-overtone band transitions of NH_3

A sensitive dye-laser spectrometer is constructed to observe the Stark effect of weak-overtone transitions in NH(3). A DeltaP/P sensitivity of 10(-6) is achieved with the help of a laser-noise-reduction system. A relatively short (30-cm) and narrow-gap (0.25-mm) Stark electrode makes it possible to apply a high electric field on molecular gas at low pressure (~1 Torr). The Stark components of the upsilon = 5 overtone band transitions of NH(3) are well resolved. The rotational assignments are confirmed, and the dipole moment in the upsilon = 5 excited vibrational state is determined to be 1.40 +/- 0.02 D.

Electronic absorption spectroscopy of molecular ions in plasmas by dye laser velocity modulation: The A←X system of N+2

A computer controlled velocity modulation dye laser spectrometer is used to measure the A 2Πu←X 2Σ+g (7,3) band of N+2. The Doppler-limited absorption spectra are fit to a model Hamiltonian to obtain precise parameters for the states. The ion rotational temperature was determined to be 461±11, and the translational temperature was estimated to be near 1200 K.

New ultra-high resolution dye laser spectrometer utilizing a non-tunable reference resonator

A new dye laser spectrometer utilizing a non-tunable reference resonator is described. The resonator consists of two Zerodur mirrors optically contacted to a Zerodur spacer. Frequency scanning of the laser is provided by acoustooptic modulation. Residual drifts of the resonator frequency — measured on line — are compensated automatically by corresponding corrections of the modulation frequency. The stability during several hours and the resettability of the dye laser frequency are±2.5 kHz and±10 kHz, respectively.

Optogalvanic laser spectroscopy of flames

The authors describe a technique for the laser spectroscopy of metal vapors which involves the evaporation, combustion, and ionization of a metal salt in a flame placed within the resonator of a dye laser spectrometer. The technique is based on the premise that at the moment that a laser pulse passes through the flame, the concentration of ions and electrons between the two electrodes placed in the flame changes, resulting in a current pulse in the measuring circuit. The technique is both mathematically and experimentally verified by testing for the detection limits of lithium, europium, and samarium.

Two-photon excitation spectrometer for dilute gases

A two-photon excitation spectrometer which can be used with dilute molecular gases is described. The spectrometer is based on a standing wave tunable dye laser synchronously pumped by a mode-locked Ar+ laser. Two-photon excitation is enhanced in two ways. First, excitation is carried out intracavity at a focus produced by a pair of spherical mirrors. Second, nonlinear absorption is further enhanced by temporal compression of the laser power through mode locking the Ar+ pump laser and synchronously pumping the dye laser. The performance of the synchronously pumped intracavity focused (SPIF) dye laser spectrometer is analyzed by measuring the two-photon excitation spectrum of naphthalene vapor and comparing it with previously measured spectra. Two-photon excitation spectra of naphthalene measured with SPIF have signal-to-noise ratios that significantly surpass those of spectra found in the literature. It is estimated that for 1 Torr of gas whose fluorescence yield is unity, a two-photon absortivity of order 10−56 cm4 s photon−1 molecule−1 would produce a photon count rate of 1 Hz. This high sensitivity is partly due to the stability of the cw design of the dye laser and the high intracavity powers. This stability and the ease of its operation makes SPIF an especially useful spectroscopic tool.

The S 1 and T 1 transient absorptions of 10-substituted acridin-9-ones measured by nanosecond laser spectroscopy

The transient absorption behaviour of 10H-acridin-9-one and the 10-alkyl-substituted derivatives has been investigated with a nanosecond dye-laser spectrometer. The S 1-S n and T 1-T n absorptions were compared in solutions of ethanol, cyclohexane and PMMA, with and without time delay of the spectroscopic beam.

色素レーザ分光計と波長安定化

色素レーザ分光計と波長安定化

Determination of polycyclic aromatic hydrocarbons in unfractionated solid solvent-refined coal by matrix isolation fluorescence spectrometry

An untreated solid solvent-refined coal sample yields matrix isolation fluorescence spectra suitable for identification and determination of polycyclic aromatic hydrocarbons. Selective excitation of fluorescence in Shpol'skii matrices and background suppression using the time resolution capabilities of a dye-laser spectrometer permit the unambiguous identification of PAHs including benzo(a)pyrene. Determination of four polycyclic aromatic hydrocarbons (benzo(a)pyrene, perylene, benz(a)anthracene, and benzo(b)fluorene) in Solvent Refined Coal I is reported, as is the determination, by identical spectrometric technique, of the benzo(a)pyrene content of a NBS shale oil standard reference material. 5 figures, 2 tables.

Dye laser spectrometer for ultrahigh spectral resolution: design and performance

A dye laser spectrometer for ultrahigh spectral resolution is described. The laser frequency is stabilized to the side of a transmission fringe of an optical cavity by means of the usual differencing servo technique. With an intralaser-cavity AD(*)P phase modulator, driven by improved fast servo electronics, the linewidth of the jet stream dye laser was reduced to 1.8 kHz rms. With fast amplitude stabilization a 1.0-kHz line-width was observed. Good long-term stability and digital frequency scanning (with a step resolution of 1 kHz and a continuous tuning range of 900 MHz) are accomplished by transferring the long-term stability of an I(2)-stabilized He-Ne laser to the dye laser via a second optical cavity and an offset locked He-Ne laser. A drift rate of <1 kHz/min was obtained while using this dye laser spectrometer to investigate two-photon optical Ramsey fringes. A fringe width of the Ramsey features of 17 kHz has been observed, confirming for the first time the high resolution capability of two-photon optical Ramsey resonances.

Time averaging by means of a computer controlled dye-laser spectrometer

The noise characteristic of available laser sources limits the sensitivity of saturated absorption spectroscopy. Time averaging is one method to improve the signal-to-noise ratio. A computer controlled dye-laser spectrometer is described which has the capability to scan several times any selected frequency range with an absolute accuracy of ±200 kHz. The sensitivity of this system is demonstrated by measuring the isotope shift of the low abundant38Ar and by detecting a weak83Kr-hyperfine component.

Double beam intracavity laser spectrometers I. Flash lamp pumped

We describe a double beam intracavity dye laser spectrometer which is capable of a direct quantitative measurement of the absorbance of weak absorbers. The instrument is sensitive to broad band absorptions. The spectrometer can be modeled to allow a prediction of its sensitivity. Experimentally, the spectrometer reported here is about as sensitive as earlier flash lamp pumped intracavity spectrometers.

On-line computer controlled cw dye laser spectrometer for laser isotope separation

An on-line cw dye laser multichannel spectrometer is described, which can be controlled by FORTRAN. Automatic tuning of a dye laser to the wavelength of maximum excitation selectivity for photochemical isotope separation is achieved. Applying the system to the selective photoaddition of iodine chloride ICl to acetylene, an enrichment factor of37Cl in the photoproduct C2H2ICl of β=100±5 was obtained. Both stable chlorine isotopes can be enriched to more than 97% purity in a single step, starting from natural samples in both cases.

High resolution dye laser spectrometer for measurements of isotope and isomer shifts and hyperfine structure

A high resolution cw dye laser spectrometer with a frequency calibration system of 100 kHz resolution is described. Two examples of measured isotope shifts will be discussed.