Optical Spectroscopic Determination of the Zero-Field Splitting in Vibronic Levels of the Triplet State of Nitrite

We have used conventional high resolution optical spectroscopic methods to determine the principal values of the fine structure tensor for the lowest triplet state (3B1 at 18 959 cm^−1) of NO2 - in Na NO2 single crystals. From the intensities in the Zeeman spectrum we find [dformula D - E = 0.86 [plus-minus] 0.04cm[sup -1],] [dformula D + E = 0.40 [plus-minus] 0.04cm[sup -1],] where the z axis is taken as the twofold axis and E = (Z − X) / 2. From the measurement of line positions in the high-field Zeeman spectrum we find D − E = 0.84 ± 0.05cm−1,D + E = 0.41 ± 0.05cm−1. The values of D and E calculated for one-center spin–spin interaction are D − E = 0.42cm^−1 and D + E = 0.24cm^−1. The calculated ordering of the spin states is the same as that observed, but we suggest that there is significant second-order spin–orbit energy associated with the real splittings. Roughly the same splittings are seen for different vibronic levels of 3B1 associated with nu2[prime

Studies of the 3455-Å Triplet State of s-Triazine

We present a confirmation of the assignment of the 28 935-cm^−1 triplet state, 3A1[double-prime], of s-triazine. The high-field Zeeman effect is used to make this assignment which is consistent with the fact the transition is polarized perpendicular to the molecular plane. The optical spectrum at low magnetic fields yields the zero-field splitting D=−0.058±0.024 cm^−1. The sign and magnitude of D is consistent with an npi* state in which one-center spin—spin interaction is a significant feature of the zero-field splitting

Absorption and emission spectroscopies of homogeneous and inhomogeneously broadened multilevel systems in strong light fields

A method is introduced to calc., for a model set of mol. levels, the spectral line shapes expected for a variety of conventional laser expts. including absorption, hole burning, fluorescence line narrowing, and Raman scattering. The method allows the incident laser field to have arbitrary intensity. Furthermore, the effects of model gaussian or lorenzian inhomogeneous distributions are readily incorporated. Earlier results for a 2-level system are easily obtained and new results are presented for inhomogeneously broadened 2- and 3-level systems, and for the effects of pure dephasing on the strong field spectra. The differences between fluorescence and Raman in strong fields, and the effect of strong fields on the spontaneous emission of inhomogeneously broadened transitions were described. Some predictions are made regarding line narrowing expts. in the strong-field limit

Spectroscopic and line-narrowing properties of resonant sum and difference frequency generation

Three wave mixing was investigated with respect to its spectroscopic applications under fully resonant conditions. A theor. study of the appropriate 2nd order susceptibility c(2) reveals interesting features both for sum and difference frequency generation. For difference frequency generation, 2 different mechanisms are possible, 1 of which allows the observation of resonances between excited states and the study of dephasing induced coherent emission. The coherence decay rate between the 2 excited states may be measured and also its pure dephasing rate. The line-narrowing characteristics of the fully resonant c(2) were studied with respect to correlation between the inhomogeneous distribution for different levels. The line-narrowing capabilities are partly complementary for the sum-and the 2 difference frequency resonance configurations. This leads to the suggestion of new line-narrowing techniques which could provide information about type and amt. of correlation in inhomogeneously broadened systems

Mixed Magnetic and Electric Dipole Transition in s-Triazine

We have shown that the radiation pattern for absorption to the lowest energy excited singlet state of s‐triazine corresponds to that of a mixed electric and magnetic dipole transition. This was done by demonstrating, for the first time with an organic, the classic procedure of obtaining absorption coefficients for different k, ε̂, and Ĥ for a uniaxial arrangement of molecules. We find the 30 014 cm^(−1) transition of s‐triazine to be 26% magnetic and 74% electric dipole, hence the state symmetry is ^1 E in the crystal field, and ^1 E″ in the free molecule (D_(3h) )

Optical, magnetic resonance, and ENDOR studies of the nπ^* triplet state of benzophenone in mixed crystals

[No Abstract

Zeeman Effect Studies of the Triplet States of Benzene

[No Abstract

Vibrational dynamics of N-H, C-D, and C = O modes in formamide

By means of heterodyned two-dimensional IR photon echo experiments on liquid formamide and isotopomers the vibrational frequency dynamics of the N-H stretch mode, the C-D mode, and the C = O mode were obtained. In each case the vibrational frequency correlation function is fitted to three exponentials representing ultrafast (few femtoseconds), intermediate (hundreds of femtoseconds), and slow (many picoseconds) correlation times. In the case of N-H there is a significant underdamped contribution to the correlation decay that was not seen in previous experiments and is attributed to hydrogen-bond librational modes. This underdamped motion is not seen in the C-D or C = O correlation functions. The motions probed by the C-D bond are generally faster than those seen by N-H and C = O, indicating that the environment of C-D interchanges more rapidly, consistent with a weaker C-D center dot center dot center dot O = C bond. The correlation decays of N-H and C = O are similar, consistent with both being involved in strong H bonding.open141