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Microwave spectral patterns observed for the silane-water complex were found much different from those of the methane-water complex. The SiH4-H2O complex is likely to have a tightly bound structure. The effective rotational and centrifugal distortion constants: B = 3621.1193 (45) MHz and DJ = 49.84 (30) kHz led to the distance between the Si and O atoms in the complex to be 3.3 Å, much shorter than the C and O separation in the CH4-H2O of 3.7 Å, and to the silane-water stretching force constant and stretching frequency to be 2.88 N/m and 65 cm-1, respectively, which are to be compared with 1.52 N/m and 55 cm-1 of the CH4-H2O. The characteristic features of the spectra observed for the main species 28SiH4-H2O are common to those of isotopic species: 29SiH4-H2O, 30SiH4-H2O, 28SiH4-H2 18O, 28SiH4-D2O, 29SiH4-D2O, 30SiH4-D2O, 28SiH4-HDO, 29SiH4-HDO, 30SiH4-HDO, 28SiD4-H2O, 28SiD4-D2O, and 28SiD4-HDO. The observed spectra also indicate that the silane executes a threefold internal rotation about one of its four Si-H bonds, while the C2 symmetry axis of the water is bent away from the internal-rotation axis. An internal axis method analysis yielded an estimate of the internal-rotation potential barrier V3 to be 140 ± 50 cm-1, and those based on diagonalization of a principal axis method Hamiltonian matrix and on the extended internal axis method resulted in V3 ranging from 180 to 100 cm-1, depending on the isotopic species studied. All the measurements were done by using a pulsed nozzle Fourier transform microwave spectrometer, and the spectral assignments were made with the aid of the Stark effect, which yielded the dipole moment to be 1.730 (10) D. Transitions in higher energy states of the SiH4 internal rotation were observed, clearly resolved from the main lines, when the carrier gas was replaced from Ar to Ne. [ABSTRACT FROM AUTHOR]

Rotationally resolved high-resolution fluorescence excitation spectra of the 0-0 band of the &Btilde²E'←&Xtilde²A2' transition of the 15N substituted nitrate radical were observed for the first time, by crossing a jet-cooled molecular beam and a single-mode dye laser beam at right angles. Several thousand rotational lines were detected in the 15080-15103 cm-1 region. We observed the Zeeman splitting of intense lines up to 360 G in order to obtain secure rotational assignment. Two, nine, and seven rotational line pairs with 0.0248 cm-1 spacing were assigned to the transitions from the &Xtilde²A2' (υ = 0, k = 0, N = 1, J = 0.5 and 1.5) to the ²E'3/2 (J' = 1.5), ²E'1/2 (J' = 0.5), and ²E'1/2 (J' = 1.5) levels, respectively, based on the ground state combination differences and the Zeeman splitting patterns. The observed spectrum was complicated due to the vibronic coupling between the bright &Btilde²E' (υ = 0) state and surrounding dark vibronic states. Some series of rotational lines other than those from the &Xtilde²A2' (J = 0.5 and 1.5) levels were also assigned by the ground state combination differences and the observed Zeeman splitting. The rotational branch structures were identified, and the molecular constants of the &Btilde²E'1/2 (υ = 0) state were estimated by a deperturbed analysis to be T 0 = 15098.20(4) cm-1, B = 0.4282(7) cm-1, and DJ = 4 × 10-4 cm-1. In the observed region, both the ²E'1/2 and ²E'3/2 spin-orbit components were identified, and the spin-orbit interaction constant of the &Btilde²E' (υ = 0) state was estimated to be -12 cm-1 as the lower limit. [ABSTRACT FROM AUTHOR]

Rotationally resolved high-resolution fluorescence excitation spectra of 14NO3 radical have been observed for the 662 nm band, which is assigned as the 0-0 band of the B ²E' ← X ²A2' transition, by crossing a single-mode laser beam perpendicularly to a collimated molecular beam. More than 3000 rotational lines were detected in 15 070-15 145 cm-1 region, but it is difficult to find the rotational line series. Remarkable rotational line pairs, whose interval is about 0.0246 cm-1, were found in the observed spectrum. This interval is the same amount with the spin-rotation splitting of the X ²A2' (ν = 0, k = 0, N = 1) level. From this interval and the observed Zeeman splitting up to 360 G, seven line pairs were assigned as the transitions to the ²E'3/2 (J' = 1.5) levels and 15 line pairs were assigned as the transitions to the ²E'1/2 (J' = 0.5) levels. From the rotational analysis, we recognized that the 2E' state splits into ²E'3/2 and ²E'1/2 by the spin-orbit interaction and the effective spin-orbit interaction constant was roughly estimated as -21 cm-1. From the number of the rotational line pairs, we concluded that the complicated rotational structure of this 662 nm band of 14NO3 mainly owes to the vibronic interaction between the B ²E' state and the dark A ²E' state through the a2'' symmetry vibrational mode. [ABSTRACT FROM AUTHOR]