Radio-Frequency Spectrum of KBr by the Molecular-Beam Electric-Resonance Method

Abstract

It is necessary to use this form of the rate equations which involves the negative, rather than those which involve the positive exponentials [Eqs. (13) and (14) of Ref. 4J to avoid roundoff errors in the sums which would eliminate all significant figures. The averaged populations used in Eq. (0 are calculated by n=![n(±to) +exp( -=to) ·n(±to) J. (A6)In calculations for the intermediate-and high-pressure regions, the approximation can be used that nCO) =n8q THE JOURNAL OF CHEMICAL PHYSICS andn(±to) =n P , wherenPis the steady-state population with the pumping power on. This approximation speeds up the calculation greatly, as it eliminates the calculation of exp( -=-5=)t o and the solving of the homogeneous set of equations (AS). In the low-pressure region, the program calculates the complex relative amplitude both exactly and with this approximation. As the pressure is increased, the two results agree to within better than experimental error, and only the approximate calculation is carried out for subsequent higher pressures. This approximation has proved to be accurate down to 10 p..Copies of this program, on cards, together with instructions for its use and sample input data are available from the authors.The molecular-beam electric-resonance method has been used to observe the radio-frequency spectra of 39K79Br and 39~81Br ~n the J = 1 rotational state and the 11=0, 1, and 2 vibrational levels. Analysis of the spectra has given dipole moments and hyperfine interaction constants of these molecules.

Hyperfine spectra of KBr and KI

“…The molecules KBr and KI, along with several other alkali halides, were examined by both microwave and molecular beam methods relatively early in the history of these techniques [12][13][14][15][16][17][18]. Our current experiments improve upon these early measurements by 3 orders of magnitude in the precision of the hyperfine interactions for KBr and 5 orders of magnitude for KI.…”

Fourier Transform Microwave Measurements of the Quadrupole Hyperfine Structure of NaBH4and KBH4

“…As mentioned earlier, we anticipated that the eQq constants of an alkali metal would take a value close to that in the corresponding alkali halide: 05.6698 and 04.93259 MHz for 23 Na in NaCl (19,20) and NaBr (21), respectively, and 05.656 and 05.0151 MHz for 39 K in KCl (22,23) and KBr (24), respectively. On the other hand, the eQq constant of boron would be quite small because the BH 4 anion would take an almost tetrahedral structure.…”

Classical model for vibrationally excited alkali halides

“…The dipole moments /Ze at the equilibrium bond length are quoted in table 4 and compared with experimental data [2][3][4] ; agreement is mostly better than 5 per cent. The variation of the dipole moment with vibrational excitation is shown in figures 1 and 2.…”

“…Values of/zi and/zIi are given in table 5 and are compared with experimental data [2][3][4]. extrapolate smoothly to Be at zero excitation.…”

“…Unfortunately spectroscopic data [2][3][4] is only available for very low vibrational states (v 43). Molecular beam studies of these excited reaction products [5,6] require knowledge of the dipole moments and rotational constants for their interpretation [7].…”