Gene A. Capelle

Reactions of germanium vapor with oxidizers: Photon yields and a new GeO band system

Germanium was reacted with N2O, O2, NO2, and NO in a flow system, which produced GeO. Chemiluminescence was observed from three electronic band systems of GeO: A 1Π→X 1Σ+ in the uv, a 3Σ+→X 1Σ+ in the blue, and b 3Π1→X 1Σ+ (a previously unreported system) in the near uv. Vibrational constants and Te values have been obtained for the a 3Σ+ and b 3Π1 states, and evidence is presented for a perturbation between the b 3Π (v=8) and A 1Π (v=0) states. Photon yields for each of the three GeO band systems were measured to be small (<0.1% in all cases) and to be strongly pressure dependent in the 0.5‐ to 20‐Torr region. Reaction of Ge vapor with F2 produced GeF (A 2Σ+→X 2Π) chemiluminescence with a measured photon yield of 6.8×10−4; the flames from Ge+Br2 and Ge+Cl2 were too weak to measure.

Chemiluminescence Spectra and Photon Yields for Several Sn-Oxidizer Reactions

Tin vapor has been reacted with N2O, NO2, O2, and F2 to produce SnO and SnF in a flame. Reactions of Sn with O2 and NO2 produced very weak chemiluminescence, whereas Sn+Br2 and Cl2 produced no detectable light emission. The highest photon yield measured was 6.7% for SnO emission that resulted from the reaction of Sn+N2O in Ar at a Sn concentration of 3×1013/cm3. The maximum SnF yield measured was 0.3% for Sn+F2. The spectral character of the SnO chemiluminescence generated in the Sn+N2O reaction was found to be a strong function of pressure (0.5–25 Torr) and carrier gas identity (Ar, He, N2) in the flow‐tube reaction system. Extension of the SnO a–X system yielded the following constants (all in cm−1): a3Σ+(1): Te=20622.6±2.5, ωe=554.0±1.7, ωexe=2.45±0.36 and X1Σ: ωe=823.40±0.99, ωexe=3.77±0.10.

Analytical photon catalysis: Measurement of gas phase concentrations to 104/cm3

A new analytic technique was developed to determine quantitatively the concentration of gas‐phase species at concentrations well below the measurement capabilities of atomic absorption and mass spectroscopy. The method involves injecting an excess of an energetic metastable species, N2(A3Σ+u) in this experiment, into a gas stream containing the species to be measured, Bi in this case. Energy transfer from the metastable to the sample species results in excitation and subsequent rapid emission of light. The intensity of the light emitted at the wavelengths characteristic of the sample species is a function of, and hence a measure of, the concentration. Concentrations as low as 1.5×104/cm3 were measured. Greater sensitivity is possible with more efficient optical detection.

Photon yields of several reactions producing diatomic strontium oxide and halides, and SrO (A′ 1Π–X 1Σ): A new band system

Strontium atoms were reacted with N2O, O3, O2, NO, Br2, Cl2, and F2 in a flow system to produce the diatomic oxide or halide. Photon yields were measured from these reactions in a bath of argon at pressures of 1.1–9.5 Torr. Photon yields in excess of 6×10−2 for the SrO A 1Σ–X 1Σ band system were observed with both N2O and O3. The total photon yield with F2 producing SrF is also high, exceeding 1×10−2, most of which is due to A 2Π→X 2Σ photons; the B 2Σ, C 2Π, D 2Σ, and E 2Π→X 2Σ systems are also observed, but they give progressively smaller contributions to the total yield. The previously unobserved SrO (A′ 1Π–X 1Σ) band system was seen in chemiluminescence from Sr+O3 and Sr+N2O reactions. Bandhead measurements allowed determination of molecular constants. The constants that correspond to the most probable SrO A′ 1Π vibrational numbering are ν00 = 9310(8), ωe = 472.8(14), ωexe = 2.06(6), Be = 0.2565(20), and αe = 0.0017(3) cm−1.

Metastable transfer emission spectroscopy-method and instrument for detection and measurement of trace materials in gas flows.

A simple and relatively inexpensive new technique for qualitatively and quantitatively measuring various gas-phase species in a flow and the apparatus for implementation are described. Detection of atomic species has been demonstrated from concentrations greater than 10(10) atoms/cm(3) to approximately 10(4) atoms/cm(3). Several classes of molecules can also be detected quatitatively with the method, although with somewhat reduced sensitivity. The method, metastable transfer emission spectroscopy (MTES), is particularly useful in materials analysis. Possible applications including the analysis of gas, liquid, and solid samples and the determination of vapor-pressure curves are discussed.

Near‐resonant electronic energy transfer from NF (a1Δ) to Bi

The rate constant for the near‐resonant electronic energy transfer process NF(a 1Δ)+Bi(4S3/2) → NF(X 3Σ) +Bi(2D3/2)+16 cm−1 has been measured to be 1×10−9 cm3 molecule−1 sec−1. The effective cross section (∼200 A2) is one of the largest that has been measured for such a process, and cannot be accounted for in terms of a long‐range interaction between charge distributions.

KrF-laser-pumped tunable dye laser in the ultraviolet

Tunable laser emission in the 335–346‐nm region has been obtained from a 0.01M solution of p‐terphenyl in p‐dioxane. The dye laser was excited by a 20‐nsec pulse from a Blumlein‐driven KrF laser oscillating at 249 and 250 nm.

Chemiluminescence of Si + N2O flames

Spectra of the chemiluminescent flame produced by the reaction of silicon vapor with N2O have shown strong emission from the A1Π-X1Σ+, b3Π-X1Σ+, and a3Σ+-X1Σ+ systems of SiO with preferential excitation into the b3Π state. Bandhead measurements of 33 bands of the b-X system yielded the following constants for the b3Π state: Te=33947.0±1.9cm−1;ωe=1013.8±1.1cm−1;ωexe=7.57±0.12cm−1 . From partially resolved rotational structure in the a-X bands, an approximate value of B = 0.59 ± 0.01cm−1 was obtained for the a3Σ+ state. The effect of adding active nitrogen and CO to the flame was investigated and the results were shown to be consistent with assigning the a and b states as triplets. The photon yield of the Si + N2O reaction was measured and found to be small.

Resonance ionization spectroscopy measurement of vapor pressure of rubidium iodide

Resonance ionization spectroscopy has been used to measure vapor pressure data for a solid (RbI) to very low pressures. A pulsed UV laser was used to dissociate RbI molecules in the vapor phase established over a sample at known temperature. The rubidium atoms were then ionized by a two‐step process using a dye laser tuned to either of two allowed transitions in the ground‐state atomic Rb system. These measurements have extended the RbI vapor pressure versus temperature curve approximatelly 10 orders of magnitude below previously reported experimental data. Although this experiment is limited to RbI, the technique is applicable to a wide variety of solids, both atomic and molecular.

CN production efficiencies from active nitrogen-hydrocarbon flames

Various hydrocarbons have been reacted with active nitrogen in a supersonic flow system. The resulting chemiluminescence was invariably dominated by CN A doublet Pi and B doublet sigma(+) to X doublet sigma(+) emission. The intensity of this emission and the excited-state vibrational temperatures were strongly dependent upon the reactant hydrocarbon. Photon yields as high as 18.5% were measured for CN A doublet Pi to X doublet sigma (+) emission when C2F4 was used as a reactant, which makes this system a very promising chemically pumped laser. Calculations have shown that, if the populations in the electronically excited states can be vibrationally cooled, it should be possible to achieve positive gain in the system. (GRA)