Rotational or rovibrational spectra of the free radicals NH(,2), BO(,2) and NO(,2) have been taken using various high resolution laser techniques.
The hyperfine structure of the u state of NH(,2), tentatively assigned as 2(,20), J = 3/2, (')X('2)B(,1) (0,13,0), has been obtained from an analysis of the microwave optical double resonance signals which occur between the u state and the J = 1/2 spin component of 1(,10) in (')A('2)A(,1) (PI)(0,10,0). The similarity of the ('1)H hyperfine splittings in u with those of the 2(,20), J=3/2 rotational level of the (')X('2)B(,1) (0,0,0) state supports the assignment of u to a highly excited vibrational state of (')X('2)B(,1). The ('14)N hyperfine splittings were found to be about 1 MHz. These splittings are considerably smaller than those of 2(,20) (')X('2)B(,1) (0,0,0). This difference has been attributed to the fact that the hyperfine coupling constants of (0,13,0) must be averaged over a large amplitude bending vibration and to the presence of borrowed (')A('2)A(,1) character in the u state.
The hyperfine structure of 37 R-branch transitions involving several vibronic bands in the ground and excited electronic states of ('11)BO(,2) has been observed with intermodulated fluorescence detection saturation spectroscopy. Stabilization of the dye laser and the elimination of spectral power broadening has permitted the achievement of linewidths of better than 10 MHz. A set of hyperfine constants for both electronic states has been determined from the observed splittings.
The (nu)(,1) + (nu)(,2) + (nu)(,3) combination band of NO(,2) has been investigated using a color center laser spectrometer with magnetic rotation sensitivity enhancement. The electron spin fine structure of this band has been resolved for the first time. The fine structure constants obtained for (1,1,1) expressed as differences from the corresponding ground state values are (DELTA)(epsilon)(,aa)=0.0115(5), (DELTA)((epsilon)(,bb) + (epsilon)(,cc))/2= -3.6(11) x 10('-5), and (DELTA)(DELTA)(,K)('s)= -4.0(6) x 10('-5) in cm('-1). Analysis of the magnetic rotation spectrum in combination with the previous high resolution data provides improved K dependent rotational (A) and centrifugal distortion constants ((DELTA)(,K), H(,K), (DELTA)(,NK), and H(,KN)). The lineshapes in magnetic rotation were observed to depend significantly upon the experimental conditions. These lineshape effects limited the accuracy of the magnetic rotation data and suggest a need for precise control of operating conditions.