Jens H. Høg

Microwave spectrum and planarity of nitrobenzene

Abstract The microwave spectrum of nitrobenzene has been reinvestigated. Transitions in the ground state and three torsionally excited states have been assigned. It is shown that the nitrobenzene molecule is planar in the ground state. The torsional frequency (50 ± 15 cm −1 ) and the barrier to internal rotation (1000 ±500 cm −1 ) have been derived from the inertial defect and the relative intensity of transitions in torsionally excited states.

Microwave spectra of isotopic thiazoles. Molecular structure and 14N quadrupole coupling constants of thiazole

Abstract Microwave spectra of thiazole and the eight monosubstituted isotopic species have been investigated. For the parent and four substituted species the 14 N hyperfine structure was analyzed and the nuclear quadrupole coupling constants determined. These coupling constants were used to derive center frequencies for all except the 15 N species. The rotational constants were computed by least squares in the rigid rotor approximation. The substitution structure of thiazole is given and discussed. Except for the N,C(4) bond and its nearest angles, the thiazole molecule is very well described as a 1:1 composition of thiophene and 1,3,4-thiadiazole.

Stark effect in KCrO3Cl

The Stark effect has been measured on four lines in the crystal spectrum of KCrO3Cl. The two lines found at 5476 A and 5379 A represent 0-0 transitions to a split 1 E(C 3n ) state. From the directions of the permanent dipoles in the two excited states it is concluded that both states are distorted relative to the ground-state geometry. No indication of a resonance interaction in the unit cell was found.

Pseudo-stark splitting of charge transfer transitions of KCrO3Cl

Abstract A linear pseudo Stark splitting has been observed for the 5476 and 5379A˚sharp line origins found in the spectrum of KCrO 3 Cl. The effect is large (2.5 and 3.2 cm −1 for 10 5 V/cm) and promises to be an important new probe in the study of charge transfer transitions.

Electric field effect on the optical absorption spectra of V3+, Cr3+ and Co3+ in α-Al2O3

Abstract Pseudo-Stark splittings have been measured for optical transitions of V3+, Cr3+ and Co3+ in corundum (α-Al2O3) when these crystals are submitted to dc and ac fields. Quantitative results have been obtained for dc electric field parallel to the C3-axis. With the electric field perpendicular to the C3-axis linear effects have been observed, both in ac field and dc field for Co3+ -(α-Al2O3); only in ac field for V3+ -(α-Al2O3). A quadratic effect is also obtained for the U-band of Cr3+ -(α-Al2O3) for Eac ⊥ C3. A comparison with previous results is made and an interpretation for a perpendicular effect is proposed.

The microwave spectrum of MnO3F

Abstract The microwave spectrum of MnO 3 F has been remeasured and several corrections and new results have been obtained: B 0 = 4129.141 MHz, D J = 1.12 kHz, D JK = 1.87 kHz; α 3 B = 8.622 , α 5 B = − 11.994 , α 6 B = 6.042 , | q 5 | = 16.005, and | q 6 | = 8.456 MHz.

Stark effect of optical spectra with an ac electric field. Application to the pair spectrum of ruby

Abstract An experimental set-up for the recording of optical spectra modulated with an ac electric field is described. The method is applied to the pair spectrum of ruby where the established assignment is conclusively confirmed.