Formation of the B³Π(0⁺) states of BrF and IF by atom recombination in the presence of singlet (¹Δ_g,¹Σ+g) oxygen

Abstract

Combination of F 'P+ with Br 'P+ or I 2P+ ground state atoms in the presence of singlet O2 'Ag, 'Xi, leads to formation of BrF B311(O+) or IF B311(O+), which were detected by observation of their band emission spectra (975>A>483 nm), B311(O+)+X1C+. It was shown that formation of BrF B311(O+) explicitly requires energy transfer from 0, 'Ag or 'Xi. The most probable excitation process is envisaged to occur by combination of Br "P+ + F 'P+ atoms (in the presence of a third body) to give BrF A311(l) (or possibly 311(2, 0-)), followed by collisional energy transfer from singlet oxygen with BrF A311(l) to BrF B311(O+).At least 38 new bands of the B+Xsystem of BrF have been identified, and the previously uncertain vibrational numbering of the B311(O+) state has been confirmed. Vibrational constants are reported for the first time for levels of the XIZ+ ground state up to v" = 10, corresponding to an energy of 6262 cm-' above v" = 0. The available data on the dissociation energy of BrF are briefly surveyed, and a value of Do (BrF) = 2.384 eV is favoured.For the B+X system of IF, many new bands have been observed, and vibrational constants for levels up to v" = 19 (10 381 cm-' above v" = 0) of the ground state are reported.Rotational analyses of the spectroscopically interesting 311t XIE+ absorption systems of the diatomic interhalogens have been made in detail for IBr,l ICI and BrCl.3 For the corresponding fluorides, ClF, BrF and IF, similar studies have not so far been undertaken, probably because of the extreme experimental difficulties. However, some vibrational analyses of CIF 311(O+)tX1Z+ 4 3 and BrF 3rI(l, 0+) c X I Z + 6* have been reported. A more promising approach is the use of emission spectra, and Durie has described the spectra of BrF and IF in emission from flames of Br, or I2 burning in F2,* as well as a rotational analysis of 24 bands of the 311(0+)-X'Z+ system of IF from a similar s o u ~c e . ~ The spectroscopy of all three molecules (ClF, BrF and IF), however, is still incomplete compared with that of IBr, IC1 and BrCl, whilst considerable uncertainties in the dissociation energies of these molecules, especially of BrF and IF, remain.In the present work, atom combination (of Br+F, and I+F) in the presence of singlet oxygen lAg, l Z : was found to give extensive band systems in emission due to the B311(O+)-X1E+ transitions of BrF and IF. The first data on the higher vibrational levels of the XIE+ ground states of BrF and IF are reported. EXPERIMENTALThe spectroscopic investigations were carried out with a fast-flow system (fig. l(a)), which was provided with two side-arms, around each of which was fitted a microwave discharge cavity. Atom flows in argon or oxygen carriers from the discharges were mixed and pumped at 150 N m-z total pressure along the flow tube. Ground-state F 'P atoms were produced by dissociation of Ar (B.O.C. 99.995 %)+CF4 (Air Products Ltd.) mixtures l o in discharge B ' . The second discharge (B) was used to produce flows of Br 2P+ or I 'P+ atoms by reaction

Chemiluminescent reactions of oxygen fluoride. 2. Reactions producing excited bromine fluoride and iodine fluoride

“…20 Our observations of analogous reactions producing excited IF offer some further insight regarding this point (see below by atom recombination may be pumped to the B state by singlet molecular oxygen (among other possible explanations for their results). 3 The pumping mechanism of the I-02F-02* reaction may therefore be fundamentally different from the mechanism of the analogous bromine reaction, possibly resulting in a higher photon yield for the B -*• X transition. IC1 was chosen as the source of iodine atoms for our initial experiments on the I + 02F reaction.…”

Chemical generation of electronically excited ClF*(B3.pi.0+) and the B .fwdarw. X emission spectrum

“…This is to be compared with a theoretical value p = 0.9904. A more precise value of p can be determined from the data, however, using a treatment recently discussed by Coxon and Wickramaaratchi.18 The isotope shift bv can be described by the approximate expression (i-p) iv'+ %)-(«'+ y2) (su (1) bv AG?…”

“…In recent years there has been considerable interest shown in the electronic characteristics of diatomic interhalogens. [1][2][3][4][5][6][7] The complexities of curve crossings among the excited electronic states of these species and the various possible correlations with states of the dissociated atoms present interesting spectroscopic problems. 5 In addition, diatomic interhalogens have been identified as candidate species for electronic transition lasers owing to favorable Franck-Condon shifts and the metastability of the lower lying excited electronic states.…”

The Diode Laser Spectrum of Iodine Fluoride (IF)in the Ground Electronic State

“…Since then there have been a number of studies of the electronic spectra of this molecule [10][11][12][13][14][15][16]. The ground state rotational spectrum was first observed by Tiemann et al [17] and independently by McGurk and Flygare [18], Recently Nair and Hoeft [19] extended these measurements into the mm-wave region and thus improved the accuracy of the number of the molecular parameters.…”