Andrew Kaldor

Pollution Monitor for Nitric Oxide: A Laser Device Based on the Zeeman Modulation of Absorption

The Concentration of nitric oxide can be monitored by a new device in which the Zeeman effect is used to shift an absorption line of nitric oxide into coincidence with a laser line of carbon monoxide. The absorption is modulated by a small, oscillating magnetic field. This device is specific for nitric oxide and is not subject to interference from other gases.

Infra-red laser enhanced reactions: chemistry of vibrationally excited O3 with NO and O2(1Δ)

Abstract Vibrationally excited ozone, produced by absorption of CO2 laser radiation, was found to react significantly faster with NO and O2(1Δ) than thermal ozone. Using a modulation technique, absolute and relative rate constants at 300K for the following reactions were calculated assuming rapid equilibration between the three closely spaced vibrationally excited levels of O3, and that only the lowest level of these, the ν2 bending mode, is active in reaction. k1′ + k2′ = 2.7 × 10−13 cm3 molecule−1 s−1; (k1′ + k2′)/(k1 + k2) = 16.2 ± 4.0; k1′/k1 = 4.1 ± 2.0; k2′/k2 = 17.1 ± 4.3; k7′/k7 = 38 ± 20. These rate constants must be modified if a different combination of vibrationally excited levels is involved. The fraction of vibrational energy usable in chemical reaction was found to be about 15, 50 and ∼ 100% respectively for processes 1′, 2′ and 7′. Our measurements clearly differentiate between the participation of vibrational energy and thermal energy but do not distinguish differences between the individual vibrationally excited states. Details of the modulation technique, involving chemiluminescence detection of NO2 and resonance fluorescence detection of oxygen atoms, are described. Comparison of our results with a previous measurement of the summation reaction (1′ + 2′) shows excellent agreement.

Infrared laser enhanced reactions: Spectral distribution of the NO2 chemiluminescence produced in the reaction of vibrationally excited O3 with NO

Vibrationally excited ozone, produced by CO2 laser radiation, was found to react significantly faster with NO than does thermal O3. The emission spectrum of the laser enhanced chemiluminescence from this reaction was measured from 520 to 810 nm. The lowest lying 12B2 state was identified as the primary source of NO*2 emission in the NO+O3 reaction. One quantum of vibrational excitation in the reactant O3 was found to introduce one quantum of vibrational energy in the product NO2 (12B2). The rate enhancement of the reaction channel producing NO2(12B2) as a result of vibrational excitation of O3 was 5.6±1.0. Thus, only about 50% of the available vibrational energy is used to enhance this reaction.

The assignment of ν2 and ν4 of SO3

Three experiments have been performed to resolve an uncertainty in the assignment of ν2 and ν4 for SO3: (i) the gas phase Raman spectrum has been measured; (ii) the infrared active combination band ν3 + ν4 has been measured; (iii) a band contour calculation has been performed taking account of the l-type resonance in ν4 and a strong Coriolis resonance between ν2 and ν4. These experiments establish beyond any doubt that ν2 lies at about 497.5 cm−1 and ν4 lies at about 530.2 cm−1. The contour calculation also shows that the Coriolis resonance gives rise to a positive intensity perturbation.

High resolution infrared spectrum and the molecular structure of sulfur trioxide

Abstract The 2v 2 3 ( E ) band of sulfur trioxide has been measured with a resolution of 0.03 cm −1 . The analysis of this band yields a set of rotational constants which fit the data to within a standard deviation of 0.003 cm −1 (which is the expected error limit). From the rotational constant B o = 0.34857 ±0.00006 cm −1 the S-O bond distance is found to be r 0 = 1.4198±0.0002 A. This value is in agreement with earlier infrared measurements, but represents a considerable improvement in accuracy.

A laser enhanced reaction technique for the measurement of V→T deactivation rates: Deactivation of vibrationally excited O3†

Abstract Rates of V→T transfer for vibrationally excited ozone (O 3 † ) in the (100), (010) and (001) levels have been measured using a laser enhanced chemiluminescent method for the deactivating gases He, Ar, H 2 , N 2 , O 2 , H 2 O, CO 2 , SO 2 , CH 4 , and SF 6 . The method takes advantage of an enhanced reaction rate between O 3 † + NO producing electronically excited NO 2 and uses the NO 2 chemiluminescence as a tracer for the O 3 † concentration. Results obtained by this new method are compared with recent results obtained by an IR fluorescence method. Good agreement is obtained for all gases, except methane, and implications of these results on the mechanism for deactivation are described.

INFRARED LASER ENHANCED REACTIONS: O3 + SO

Vibrationally excited ozone, O3†, produced by CO2 laser radiation was found to react with SO significantly faster than thermal ozone via the chemiluminescent reaction process O3+SO→SO2(1B1) +O2(3Σg). The vibrational rate enhancement of this reaction was 2.5±0.6 at 300 K. This represents the utilization of 27% of the available vibrational energy to promote the reaction based on a model assuming involvement of a single vibrational mode. The laser enhanced chemiluminescence measured from 260 to 450 nm was found to exhibit a 630±200 cm−1 blue shift. This is interpreted as a partitioning of the available vibrational energy of O3† in the vibrational manifold of the SO2(1B1) product.

Absorption Spectrum of Borazine in the Vacuum Ultraviolet

The absorption spectrum of both vapor‐phase and matrix‐isolated borazine has been investigated in the 2000–1500‐A region. Three electronic transitions have been observed. The strongest absorption, with a maximum at 1650 A, is assigned to the allowed 1E′−1A1′ transition. Two weaker absorptions, with forbidden origins at 1975 and 1889 A, are assigned to the forbidden transitions 1A2′−1A1′ and 1A1′−1A1′, respectively. The 1A2′−1A1′ transition is made vibronically allowed by one quantum change in the ν16 and ν17 e′ vibrations. The vibration making allowed the 1A1′−1A1′ transition could not be determined.

Infrared laser modulated molecular beam mass spectrometry

Abstract A technique is described whereby a modulated beam can be extracted from gas mixtures which are ex- xited by infrared laser radiation. The method has been applied to time resolved mass spectrometric studies of laser induced molecular processes for systems containing BCl 3 and SF 6 as radiation absorbers, and shows general applica- bility to studies of laser induced chemical reaction.

Infrared laser enhanced reactions: V→V and V→T energy transfer in the O3SiF4O2 system

Abstract Rapid V→V energy transfer between SiF 4 and O 3 has been observed following laser excitation of either O 3 or SiF 4 . A CO 2 laser tuned to either the 9.6 μ P(30) or P(32) transitions was used to promote vibrational excitation in O 3 and SiF 4 , respectively. In experiments employing the P(32) transition, the V→V transfer to O 3 and subsequent reaction of O 3 † with NO were used to obtain the rate constant of V→T deactivation of SiF 4 † by O 2 . Fractional modulation measurements of the chemiluminescence generated by the O 3 + NO reaction were used in experiments employing the P(30) transition to obtain a rate constant for the V→V energy transfer between O 3 † and SiF 4 .