Magnetic and electric deflection analysis of the scattering of Cs + NO2 shows that the principal product is a paramagnetic, polar molecule. Magnetic analysis of the K + NO2 system indicates that the scattered signal is paramagnetic; a similar study of Na + NO2 shows a small yield of diamagnetic product. For the analogous reactions with CH3NO2, the product is diamagnetic and has a pseudo-first-order Stark effect. From these data and thermochemical arguments the principal alkali-containing products are identified as: for Cs + NO2, a 2Σ electronic state of CsO; for Na + NO2, probably a 2Π state of NaO; for M + CH3NO2, almost certainly MNO2 in a singlet state. The NO2 results indicate that the ground state of the MO molecule changes from 2Π for LiO (the only species which had been previously observed) to 2Σ for CsO. The usual differential surface ionization detection fails for Cs + NO2 and consequently only a very rough estimate of the scattering is obtained; this indicates that the total reaction cross section is ∼ 100 Å2. For the CH3NO2 reactions differential surface ionization is applicable. Again the reaction cross sections are ∼ 100 Å2 and increase as Na→K→Cs. The c.m. product angular distribution is broad, with about the same intensity in the forward and backward hemispheres. These results are discussed in terms of the electronic structure of the reactant and product molecules and contrasted with reactions of alkali atoms with halogen-containing molecules. Scattering of related molecules has also been studied briefly, including RONO and R′ONO2 (with R = i-C5H11 and R′ = C2H5), which give diamagnetic products with yields very similar to CH3NO2, and N2O and R″OOR″ (with R″ = t-C4H9), for which only paramagnetic species were observed.

Crossed-beam studies have been made of the reactions of K, Rb, and Cs atoms with Br2 and of K and Cs with Iz. It is found that for all these systems: (1) The reaction cross sections are remarkably large, :> 150 A2.(2) Most of the alkali halide product recoils into the forward hemisphere with respect to the incident alkali atom beam, with scattering angle 0< 60° (in the center-of-mass system). However, there also appears to be considerable intensity (",20% of the forward peak) throughout the backward hemisphere, 90°<0<180°.(3) The angular distribution (in the C.m. system) of alkali atoms scattered without reaction falls off much more rapidly at wide angles than for collisions between unreactive molecules of comparable size. (4) The shape of the angular distributions of both the reactive and nonreactive scattering is the same for various alkali metals, but differs appreciably for Br2 and Iz. (5) Most of the chemical energy released appears as internal excitation of the products. This could include substantial rotational and/or electronic excitation, but other evidence shows that vibrational excitation of the newly formed bond is dominant. All these properties can be accounted for by a model (suggested originally by Polanyi and Magee) which assumes that the attacking alkali atom transfers its valence electron to the halogen at large distances

This paper constitutes the final report from our laboratory on crossed beams exploratory studies of the chemistry of gaseous alkaline earth atoms (M). Measured product laboratory angular distributions and derived center-of-mass (CM) recoil distributions are presented for Ba + SFe, Ba and Sr + PCI3, Sr and Ca + N02, Ba and Sr + (CH3)2CHNC>2, and Ca + CC13N02; in addition, qualitative results are presented for Ba, Sr, and Ca + SnCR and Ba + S02. All derived CM product angular distributions are asymmetric, favoring scattering into the forward hemisphere (i.e., 0°< < 90°, where = 0°is defined by the initial M velocity), except for Ba + SFe, where the CM distribution is approximately symmetric about = 90°. This suggests that the Ba + SFe reaction proceeds via formation of an BaSFe complex with a lifetime (tc) greater than its rotational period (rr), whereas the PCI3, N02, (0 3)2 2, and CC13N02reactions proceed via direct mechanisms with rc < rr. For SFe, PCI3, and N02, the qualitative behavior of the alkaline earth reaction parallels that previously reported for the analogous alkali (A) reaction.However, no evidence of an MSnClg product from + SnCU is observed here, whereas ASnCl3 is thought to be an important product of K, Rb, or Cs + SnCLt. Also, MO is apparently the product of Ba or Sr + (CH3)2CHN02 in contrast to the CsN02 product formation reported for Cs + CH3N02.Earlier papers in this series reported results of crossed beams studies of reactions of alkaline earth atoms with HI,la halogen molecules, lb-c and some halides of methane.ld The present paper reports on the remainder of our exploratory studies of gaseous alkaline earth atom chemistry; results are presented for reaction of Ba, Sr, and/or Ca with some inorganic halides (SFe, PC13, and SnCLt) as well as some oxygen-containing compounds (N02, S02, (CH3)2CHN02, and CCI3NO2). Here again, reactive cross section are characterized only semiquantitatively, the primary intention being to compare the chemical behavior of alkaline earth atoms (M) with that previously reported for alkali atoms (A).