The parity of rotational levels

The parity of rotational levels of polyatomic molecules is discussed by using the permutation-inversion group of Longuet-Higgins.     

Radiofrequency spectroscopy inside a laser cavity: Nuclear quadrupole resonance and A1-A2 splitting of CH3Br

The highly sensitive method of infrared-radiofrequency double resonance inside a CO₂N₂O laser cavity has been applied to the observation of “pure” nuclear quadrupole resonance and direct A₁-A₂ transitions of CH₃Br. More than 150 quadrupole resonances have been observed for ¹²CH₃⁷⁹Br, ¹²CH₃⁸¹Br, ¹³CH₃⁷⁹Br, and ¹³CH₃⁸¹Br using direct double resonance as well as collision-induced satellites. Accurate hyperfine constants, i.e., the quadrupole coupling constant eqQ and its rotational dependence χ_J and χ_K, Hougen's coefficient χ_d, and the spin-rotation constants C_N and C_K have been determined for the ground state. The eqQ in the excited states ν₃, ν₆, ν₃ + ν₆, and 2ν₆ have also been determined. About 60 direct l-doubling transitions have been observed, which has enabled us to determine the l-doubling constant q_v(1,1), its rotational dependence δq_v^J(1,1) and the asymmetry parameter for the quadrupole coupling constant eqQη for the ν₆ and ν₃ + ν₆ states. A set of direct A₁-A₂ transitions in the 2ν₆ state with K = 1 and l₆ = ?2 and that in the ν₆ state with K = 2 and l₆ = ?1 have been observed. The rovibrational and isotope assignments of the observed A₁-A₂ are helped by the existence of quadrupole hyperfine structure and many collision-induced satellites. The rovibrational assignments of CH₃Br transitions which are coincident with laser lines are summarized.     

Determination of electric dipole moment for the ν2 vibrational state of 15NH3 by infrared-infrared double resonances

An infrared-infrared double-resonance technique, employing the sidebands produced by electro-optic amplitude modulation of a single-frequency CO₂ laser, is used to observe the second-order Stark effect of the ν₂asR(2, 0) transition of ¹⁵NH₃. The technique enables the Stark shifts in ground and vibrationally excited states to be observed separately and yields the electric dipole moments: μ(v₂ = 1) = 1.253 ± 0.003 D, μ(v = 0) = 1.469 ± 0.004 D. The relative intensity distribution, linewidths, and line shapes of features in the double-resonance Stark spectra are also examined.     

Optical spin orientation of excitons in GaSe under longitudinal magnetic field

The degree of circular polarization of the free-exciton luminescence line has been measured in GaSe excited by circularly polarized light at 4.2 K under longitudinal magnetic field. The result shows that the spin relaxation time of exciton is field-dependent but the spin memory before reaching the exciton ground state is almost unaffected by the applied longitudinal magnetic field.     

Island dynamics in the large-helical-device plasmas

In the Large Helical Device plasma discharges, the size of an externally imposed island with mode number ( n/m = 1/1) decreases substantially when the plasma is collisionless ( nu(*)< approximately 1) and the beta is finite ( > approximately 0.1%) at the island location. For the collisional plasmas with finite beta, on the other hand, the size of the island increases. However, there is a threshold in terms of the vacuum island size below which the island enlargement is not seen.     

Synthesis and anti-influenza virus activity of tricyclic compounds with a unique amine moiety

Several novel tricyclic compounds with a unique amine moiety (1, 2a--i) were designed and prepared based on the structure of triperiden for the development of anti-influenza virus agents. An in vitro antiviral assay showed that 1-(1-azabicyclo[3.3.0]octan-5-yl)-1-(4-fluorophenyl)-1-(2-tricyclo[3.3.1.1(3.7)]decyl)methan-1-ol hydrochloride (2f) has a potent anti-influenza A virus activity. Furthermore, since 2f was well tolerated in mice, 2f is promising as a novel anti-influenza virus agent for humans.