Infrared diode lasers

Even more remarkable is tlie fact tliat tliese infrared diode lasers have sufficient resolution to measure tlie Doppler... 

Figure C3.3.4 shows a schematic diagram of an apparatus tliat can be used to study collisions of tlie type described above [5, 9,12,16]. Donor molecules in a 3 m long collision cell (a cylindrical tube) are excited along tlie axis of tlie cell by a short-pulse excimer laser (typically 25 ns pulse widtli operating at 248 mil), and batli molecules are probed along tliis same axis by an infrared diode laser (wavelengtli in tlie mid-infrared witli continuous light-output...

The data obtained in tlie infrared-diode-laser-probe studies described above provides quenching infonnation at a given substrate donor energy E. By varying tlie laser excitation wavelengtli for production of vibrationally hot... 

Infrared diode laser spectroscopy has been used for the measurement of hydrocarbon and CO concentrations in exhaust (13, 14, 15). The adsorption path length, and thus the absorption cell volume, required for hydrocarbon measurement is rather large, limiting the time-resolution of the measurement. The absorption path length required for CO measurement, however, is relatively short and approximately equal to the diameter of a standard exhaust pipe. This allows CO to be measured with high time-resolution by an infrared laser beam passed through an... 

Sell, J. A. Herz, R. K. Monroe, D. R. "Dynamic Measurement of Carbon Monoxide Concentrations in Automotive Exhaust Using Infrared Diode Laser Spectroscopy" SAE Paper No. 800463, 1980. 

Infrared diode laser spectroscopy, 46 119, 148 Infrared emission, transition,-metal ions, 35 334-335... 

If near-infrared diode lasers have low-noise characteristics similar to those of mid-infrared diode lasers, and thus minimum absorbances of 10 5 or less are possible, then an approximate detection limit can be calculated for an absorption experiment. For a 200-m optical path, the calculated detection limit is 5 x 1010 molecules/cm3, which is well above levels of H02 expected to be found in the atmosphere. An absorption experiment in this spectral region apparently would require extremely long optical path lengths, and, indeed, a calculation with a 5-km path yields a calculated detection limit of 2 x 109 molecules/cm3, still rather high for tropospheric measurements. Other issues associated with the use of diode lasers in absorption spectroscopy are discussed in the next section. 

C. Yamada and E. Hirota, Phys. Rev. Lett., 56, 923 (1986). Detection of the Silyl Radical SiH3 by Infrared Diode-Laser Spectroscopy. 

Suzuki, T., Kanamori, H., and Hirota, E. (1991). Infrared diode laser study of the 248 nm photodissociation of CH3I, J. Chem. Phys. 94, 6607-6619. 

The optical apparatus used in this study was designed according to the strategy described in section 8.4.3, which permits the simultaneous measurement of birefringence and dichroism. The source was a infrared diode laser that generates light at a wavelength in the... 

Among other new methods, tunable laser absorption spectroscopy using infrared diode lasers offers prospects for improved accuracy and specificity in concentration measurements, when a line-of-sight technique is appropriate. The present paper discusses diode laser techniques as applied to a flat flame burner and to a room temperature absorption cell. The cell experiments are used to determine the absorption band strength which is needed to properly interpret high temperature experiments. Preliminary results are reported for CO concentration measurements in a flame, the fundamental band strength of CO at STP, collision halfwidths of CO under flame conditions, and the temperature dependence of CO and NO collision halfwidths in combustion gases. 

Hanson, R. K., "High-Resolution Spectroscopy of Shock-Heated Gases Using a Tunable Infrared Diode Laser" in "Shock Tube and Wave Research" University of Washington Press, 1978,... 

CIRDLS = infrared diode laser spectroscopy ES = electronic spectroscopy, spectra with resolved vibrational structure MW = microwave spectroscopy force field calculations denote harmonic frequencies obtained on the basis of combined analysis of electron diffraction and vibrational spectroscopy data. 

IRDLKS = infrared diode laser kinetic spectroscopy, investigation of the rotational structure of the l 2 band MW = microwave spectroscopy ED = electron diffraction ES = electronic spectroscopy, investigation of the rovibronic structure of electronic transitions bond angles calculated from isotopic shifts of the 03 bands of triatomic CAs are not presented here due to their large experimental error these values are reported in Section VI. 

Infra-red chemiluminescence has been used to measure the vibrational state distributions of CO2 formed by reaction on Pt and Pd surfaces [45-50]. While the detection sensitivity of infrared chemiluminescence does not approach that of LIF or REMPI, it is an attractive way to probe molecules such as CO2 where there is substantial vibrational excitation and REMPI schemes are not available. In some cases Doppler measurement of the translational energy release can be achieved, giving direct information on the translational energy release of vibrationally excited C02 [45]. Recently infrared diode laser spectroscopy has been used to detect vibrationally excited CO2 from CO oxidation over... 

Spiropyrans show promise for optical recording, three-dimensional optical memories,214 and holography.215 The dyes currently under study for these applications very probably will not be used merely dissolved in a bulk polymer matrix, but will be oriented in films and membranes, or adsorbed or vapor deposited on solid substrates to take advantage of the nonlinear optical properties of the colored forms. For example, thick (0.5 mm) PMMA films of 6-nitro-thiaBIPS can be used to record wavelength-multiplexed volume holograms with an infrared diode laser. This system is impractical at present because of fatigue and poor diffraction efficiencies.216... 

IRDLKS infrared diode laser kinetic spectroscopy... 

R.J. Holdsworth, PA. Martin, D. Raisbeck, and M.E. Pemble, In Situ, Monitoring of Atmospheric Pressure Tin Oxide CVD Using Near-Infrared Diode Laser... 

Cooper, D.E. Martinelli, R.U. Near-infrared diode lasers monitor molecular species. Laser Focus World 1992, 28 (11), 133-146. 

In our work on CO2-HX structures, tunable infrared diode laser spectroscopy was used to obtain geometries for X = F, Cl, and Br, using the CO2 asymmetric stretch chromophore [34], Both CO2-HF and CO2-HCI displayed the clear signatures of the linear equilibrium geometries that had been established previously [35, 36]. On the other hand, the C02-HBr spectrum showed that this complex is very asymmetric, which came as a surprise. We had originally assumed that C02-HBr was linear, by analogy with CO2-HF and COj-HCl. However, it is not. The observed C02-HBr spectra indicate a broadside inertial structure, with an u-axis moment of inertia close to that of uncomplexed CO2. Figures 11 and 12 show representative spectra that... 

But where does the available energy go, if not into OH V, R excitation Is it in center-of-mass (CM) translation, and/or CO V, R excitation These questions were answered experimentally by both (i) LIF measurements of nascent OH Doppler shifts, which yielded average laboratory translational energies, which in turn were converted to average CM translational energies [122], as well as (ii) infrared diode laser resonance absorption [123] and VUVLIF [124] measurements of nascent CO K R excitation. With (i), several well-resolved OH v = 0) - X H rotational transitions were... 

Relative CO2-HCI and C02-HBr concentrations were measured under conditions similar to those used in the photoinitiated reactions, but in a completely separate apparatus that used pulsed slit nozzle expansions and tunable infrared diode laser spectroscopy. This was achieved by recording fully rotationally resolved CO2-HXIR absorption spectra using the CO2 asymmetric stretch chromophore, as described in Section III.A. The rotational distributions fit temperatures quite well, usually 3K. Rotational partition functions were calculated for the measured rotational temperatures and the areas under the absorption lines recorded for all transitions. From this, relative concentrations were determined. Details are available elsewhere [139, 140]. 

Infrared diode lasers are used in compact disc players and laser printers, and in bar code readers (see Chapter 11). They are solid-state devices, typically constructed of gallium arsenide, and energy is pumped into them at a low potential... 

Valuable information on the kinetics and mechanism of CF3 + N02 comes from the experimental and theoretical study by Pagsberg et al,226 The experiments, performed using time-resolved infrared diode laser spectroscopy, were supported by ab initio calculations to provide insight into the potential energy surface of the reaction system. The reaction was initiated by pulse radiolysis of Ar/SF6/CF3I mixtures. The abstraction reaction of the iodine atom from CF3I by fluorine atoms leads to the formation of CF3 radicals. The reactions... 

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