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 Å2) 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.

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 1010 atoms/cm3 to approximately 104 atoms/cm3. 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.

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.

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.

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.

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)

BaO molecules were sequentially excited by collinearly propagating radiation from two cw lasers, an argon ion laser (488.0 and 496.5-nm lines) and a tunable (560–630 nm) rhodamine 6G dye laser. This sequential excitation technique, called optical–optical double resonance (OODR), is a special case of two-photon spectroscopy in which two visible or uv wavelength photons of different frequencies resonantly excite a molecule from an initial level (v″,J″) to a final level (v*,J*) by way of a real intermediate level (v′,J′). Two types of optical double resonance experiments were performed on BaO. The first, excitation spectroscopy, revealed 19 vibronic levels of 1Σ+ electronic symmetry between 36 490 and 38 620 cm−1 above E (X 1Σ,re). These 19 1Σ+ levels belong to two or more perturbed electronic states. No 1Π levels were found, although levels belonging to the upper state of the BaO B (1Π) –X 1Σ Parkinson bands occur in this energy region. The second type of experiment, photoluminescence spectroscopy, enabled observation of extended rotationally resolved photoluminescence progressions out of various two-photon-excited levels (v*,J*) into BaO X 1Σ (v″=0–34). Vibrational energies and rotational constants obtained from these photoluminescence progressions were used to construct an RKR potential energy curve for BaO X 1Σ+ through v″=40, from which it was shown that the X 1Σ+ and a 3Π curves cross at r=0.276 nm and E=22 750 cm−1 [above E (X 1Σ,re)]. Laser frequency jitter of less than 10−3 cm−1 resulted in large intensity fluctuations of the OODR signal, implying that the double resonance linewidth was narrower than the Doppler width of the (v′,J′) → (v*,J*) transition. This sub-Doppler width effect resulted from excitation of (v′,J′) molecules that were velocity selected relative to the laser propagation direction.

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.

Calcium atoms have been reacted with various oxidants to produce chemiluminescence of CaO, CaBr, CaCl, and CaF. Spectra of the flames were recorded, and photon yields were measured for the reactions. Photon yields of CaO at 1.2 torr vary from 6.0×10−2 for Ca+O3 to 0.04×10−2 for Ca+NO2. Ca+F2 gives yields as high as 0.9×10−2, while Cl2 and Br2 are considerably less efficient as oxidants.

Several diatomic metal halides, BaBr, BaCl, BiBr, BiCl, CuBr, CuCl, PbBr, and PbCl, were produced by reacting metal vapor with Br2 or Cl2. Molecules were identified from chemiluminescence and laser induced photoluminescence. Using a pulsed, tunable dye laser, the radiative lifetimes of the C2 II state of BaBr and BaCl were found to be 8 and 22 nsec, respectively.

A shortening of I2(B 3Π0u+) fluorescence lifetimes has been observed upon application of a magnetic field and is a function of the vibrational level of the upper electronic state and of magnetic field strengths. A suggested process is predissociation, due to mixing by the magnetic field of a repulsive Ou− state with the B state.