Diode laser spectroscopy of the SF radical

The vibration-rotation spectra of the SF radical were observed by an infrared diode laser spectrometer. The SF radical was generated directly in a cell by glow discharge in a mixture of carbonyl sulfide and carbon tetrafluoride. Zeeman modulation and discharge current modulation were employed to discriminate SF lines from many lines of the reactants and other products. Thirty two lines were assigned to the v = 1 ← 0 and 2 ← 1 bands of both ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ spin states. A least-squares analysis of all the assigned lines provided precise values for molecular parameters in v = 1 and 2 and the two band origins, where ground-state constants were constrained to microwave results. The harmonic frequency ω_e was thus determined to be 837.6418(13) cm^?1, and the equilibrium bond length r_e was calculated from the B_e rotational constant to be 1.596 244(22) Å with the error in parentheses, which included 2.5 standard deviations and the uncertainty of Planck's constant.     

Effect of basic amino acids on photoreaction of ketoprofen in phosphate buffer solution

Photoreaction of ketoprofen (KP), one of the widely used nonsteroidal anti-inflammatory drugs (NSAIDs), was studied with transient absorption spectroscopy in phosphate buffer solution (pH 7.4) in the presence of basic amino acids of histidine (His), lysine (Lys) and arginine (Arg). Deprotonated form of KP (KP(-)) excited with UV-light irradiation gave rise to carbanion through a decarboxylation reaction. It was found that carbanion abstracted a proton from the side chain of the protonated amino acids to yield 3-ethylbenzophenone ketyl biradical (EBPH); however, no reaction was observed with alanine. The relative yield of EBPH by the proton transfer reaction with His was ca. 40 times larger than that of the other two basic amino acids, suggesting that the proton-donating ability of His (protonated His) should be quite high. The information on the photoreaction mechanism of NSAIDs with basic amino acids was essential to understand primary reaction of excited NSAIDs in vivo causing photosensitization on human skin.     

The microwave spectrum of the SiCl radical

The microwave spectrum of ²⁸Si³⁵Cl, the most abundant isotopic species of the silicon monochloride radical, was observed in both the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ spin states of the ground vibronic state. The SiCl radical was produced in a flow cell by a dc discharge in SiCl₄. The observed transitions were $\text{J =}\text{7}\text{2}\text{←}\text{5}\text{2}\text{up to}\text{21}\text{2}\text{←}\text{19}\text{2}$ for both the spin states, and the observed frequencies were subjected to the least-squares analysis to yield accurate molecular constants as follows: B₀ = 7652.3048(23), D₀ = 0.007017(14), A_J = ?0.8392(16), p₀ + 2q₀ = 138.660(98), q₀ = 0.20(17), $\text{a + (b + c)}\text{2}\text{= 37.50(28)}$, $\text{a ? (b + c)}\text{2}\text{= 49.84(73)}$, b = 9(12), d = 46.40(94), and eQq₁ = ?23.13(96), all in MHz with 3σ in parentheses. The positive sign of the Λ-doubling constant, p₀, indicates that the contributions of ²Σ^? states dominate over those of ²Σ⁺ states. The spin and orbital averages of the unpaired-electron distribution were calculated from the observed hyperfine coupling constants and were discussed in terms of the electronic structure of the molecule.     

Pump-probe photoionization study of the passage and bifurcation of a quantum wave packet across an avoided crossing

The application of femtosecond pump-probe photoelectron spectroscopy to directly observe vibrational wave packets passing through an avoided crossing is investigated using quantum wave packet dynamics calculations. Transfer of the vibrational wave packet between diabatic electronic surfaces, bifurcation of the wave packet, and wave packet construction via nonadiabatic mixing are shown to be observable as time-dependent splittings of peaks in the photoelectron spectra.     

Incorporating historical information in testing for a trend in Poisson means

An exact conditional test is developed for testing a trend in Poisson means when the historical control information is incorporated into the concurrent control data. An asymptotic conditional test is also developed as an alternative to the Tarone test. Asymptotic gains by the incorporation of the historical information is evaluated.     

Structures of S-matrices for three body Schrödinger operators

Structures of the S-matrix associated with the collision process from 2 clusters to 3 clusters are studied. This S-matrix is shown to have a continuous kernel except for 2-dimensional spheres on which 2-body subsystems have zero velocity. On these spheres, the S-matrix has, in general, singularities whose existence arises from the zero eigenvalues and the zero resonances of the 2-body subsystems.     

Infrared diode laser spectroscopy of FCO: The ν1 and ν2 bands

The ν₁ (CO stretching) and ν₂ (CF stretching) bands of the FCO radical were observed with Doppler-limited resolution by an infrared diode laser spectrometer with Zeeman and source modulation. The FCO radical was generated by a 60-Hz discharge in one of the following three gas mixtures: O₂ + C₂F₄, CO + SF₆, and CO + C₂F₄, all diluted with He. The observed spectra were analyzed to determine the rotational constants, the centrifugal distortion constants, and the spin-rotation interaction constants. The band origins, 1861.6372(1) and 1026.1283(1) cm^?1 [with standard errors in parentheses], which were obtained, were found to agree well with matrix data, 1857 and 1023 cm^?1, respectively. The assignment of the observed spectra to the FCO radical was further supported by observing the ν₁ band of F¹³CO, which was obtained from ¹³CO and SF₆. The molecular structure and the force field of FCO are briefly discussed by using molecular constants obtained from the observed spectra.     

Microwave spectra of deuterated ethylenes: Dipole moment and rz structure

The pure rotational spectra of three deuterated ethylenes, CH₂CD₂, CH₂CHD, and cis-CHDCHD, were observed by microwave spectroscopy, and the rotational and centrifugal distortion constants were determined precisely. The dipole moment of CH₂CD₂ was calculated from the Stark effects to be 0.0091 ± 0.0004 D. From the observed rotational constants the average structure was calculated to be $\text{r}{}_{\mathrm{z}}\text{(CC)}\text{= 1.3391 ± 0.0013}\text{A}\text{?}$, $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{= 1.0869 ± 0.0013}\text{A}\text{?}$, θ_z(CCH) = 121.28 ± 0.10°, and $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{- r}{}_{\mathrm{z}}\text{(CD)}\text{= 0.00137 ± 0.00037}\text{A}\text{?}$, where the errors include one standard deviation in the fitting and errors due to an uncertainty (±0.03°) in θ_z(CCH) - θ_z(CCD).     

Ultrastable cesium atomic clock with a 9.1926-GHz regeneratively mode-locked fiber laser

We describe an ultrastable cesium (Cs) atomic clock with a 9.1926-GHz regeneratively mode-locked fiber laser obtained by use of an optically pumped Cs beam tube. By adopting a 1-m-long Cs beam tube with a linewidth of 110 Hz, we have successfully obtained frequency stabilities of 4.8 x 10(-12) for tau = 1 s and 6.3 x 10(-13) for tau = 50 s for a 9.1926-GHz microwave output signal. This Cs atomic clock can generate an optical pulse train with the same stability as that of the obtained microwave, which allows us to deliver a frequency standard optical signal throughout the world by means of optical fiber networks.