Ja Kang Ku

Radiative lifetimes of the FeO orange system

Abstract The ground-state FeO molecules are generated from photolysis of Fe(CO) 5 in a Fe(CO) 5 /M(O 2 or N 2 O)/Rg(He or Ar) mixture using an unfocused weak UV laser beam. The formation of ground-state FeO molecules is identified by a laser-induced fluorescence (LIF) method. The LIF signal from FeO molecules is stronger in O 2 than in N 2 O at the same partial pressures. The radiative lifetimes for seven bands in the FeO orange system are measured. They are substantially different depending on the excited band ranging from 260±30 ns to 590±50 ns.

Structure and phosphodiesterase activity of Bis-Tris coordinated lanthanide(III) complexes

A commonly used buffer, 2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (Bis-Tris) coordinates lanthanide(III) ion strongly in water to form molecular species that are highly active for the hydrolysis of a phosphate diester, bis(4-nitrophenyl) phosphate.

Direct formation of a state-selected excited state of Fe atoms by multiphoton dissociation of Fe(CO)5 at atomic transition frequencies

Abstract When an unfocused laser beam with narrow linewidth whose frequency matches exactly and atomic transition line of the Fe atom was passed through a gas mixture containing Fe(CO)5, atomic emissions from the state-selected excited state of Fe atoms were observed. The power dependence of the emission intensities as well as excitation and fluorescence spectra suggested that the state-selected excited state Fe atoms are generated by one-photon absorption of the ground state Fe atoms formed by two-photon dissociation of Fe(CO)5 within a single laser pulse.

Relaxation kinetics on the first excited singlet state of SO2 from time resolved emission spectra

Abstract The relaxation kinetics on the first excited singlet state ( 1 A 2 ) of SO 2 have been studied from time-resolved emission spectra in the 300–450 nm region. Two rovibronic levels belonging to the elements E-band and the 1 A 2 (0,8,1) level, which are located above and below the origin of the 1 B 1 state, respectively, were excited to investigate the role of the 1 B 1 state on the relaxation kinetics. Direct emissions from the laser excited rovibronic levels in the 1 A 2 state and direct intersystem crossing between the 1 A 2 (0,8,1) and 3 B 1 states were observed and revised relaxation kinetic schemes are proposed.

Collisional quenching of Ga(5p) atoms by H2, D2 and CH4

Abstract Collisional quenching of Ga(5p) atoms by H 2 , D 2 and CH 4 has been studied. The gallium atoms were generated by photolysis of trimethyl gallium using a KrF laser. The Ga(5p) state was populated by two-photon excitation from the ground state and cascade fluorescence from Ga(5s) atoms was analyzed to extract quenching rate constants for Ga(5p) atoms. The apparent quenching rate constants for Ga(5p) atoms are (4.6±0.3)×10 −10 , (3.4±0.3)×10 −10 and (7.8±0.2)×10 −11 cm 3 molecule −1 s −1 by H 2 , D 2 and CH 4 , respectively. It is found that the predominant process for the large quenching rate constants for Ga(5p) atoms by H 2 and D 2 is the energy transfer for Ga(5s) formation.

Radiative lifetimes and intramultiplet mixing rate constants for Ga(4d) atoms in Ar

Abstract Radiative lifetimes for Ga(4d 2 D 3 2 ) and Ga(4d 2 D 5 2 ) states have been investigated by a laser-induced fluorescence technique. The individual spin-orbit state of Ga(4d) atoms was formed from the Ga(4p 2 D 3 2 ) atoms generated by a pulsed discharge of a trimethyl gallium and Ar mixture. The radiative lifetimes for the Ga(4d 2 D 3 2 ) and Ga(4d 2 D 5 2 ) states are 7.5 ± 0.2 and 9.0 ± 0.3 ns, respectively, and the two states are strongly coupled in Ar. The intramultiplet mixing rate constants assigned from kinetic simulations of time profiles are (12 ± 3) × 10 −3 and (8±2)×10 −10 cm 3 molecule −1 s −1 , respectively.

Ground state Fe atom formation efficiencies from two-photon dissociation of Fe(CO)5 at 386.0, 368.0, 319.3 and 298.4 nm

Relative formation efficiencies of the ground state Fe atoms from two-photon dissociation of Fe(CO)5 have been studied using an unfocused weak laser pulse at 386.0, 368.0, 319.3 and 298.4 nm. The laser wavelengths correspond to a5D4 → z5D4, a5D4 → z5F4, a5D4 → z3F4 and a5D4 → y5D3 transition frequencies of an Fe atom. The relative amounts of Fe atoms generated by two-photon dissociation of Fe(CO)5 were obtained by comparing the emission intensities from the excited state of Fe atoms with and without a pulsed dc discharge. The relative formation efficiencies are 100:21:0.2:0.08 as the photon energy decreased.

Intersystem crossing rate constants from the (0,4,1) and (1,2,1) levels of the à 1A2 to ã 3B1 state of SO2

Collision-induced intersystem crossing rate constants from the (0,4,1) and (1,2,1) levels of the A 1A2 to a 3B1 state and rovibronic relaxation rate constants in the A 1A2 state of SO2 have been studied. The laser wavelength was set at 335.86 and 334.09 nm for the (0,4,1) and (1,2,1) excitation, respectively. When a few rotational levels belonging to the (0,4,1) and (1,2,1) vibrational levels were populated by a narrow bandwidth laser, both the fluorescence from the A 1A2 state and the phosphorescence from the a 3B1 state were observed from the time resolved emission spectra. The decay behavior of the fluorescence signal showed fast and slow components. The radiative lifetimes and apparent quenching rate constants obtained from the fast component analysis are 38±5 and (9.8±0.2)×10−10 for (0,4,1) excitation and 33±5 μs and (1.0±0.1)×10−9 cm3 mol−1 s−1 for (1,2,1) excitation, respectively. The effective lifetimes and quenching rate constants for the slow component are 280±100 and (1.5±0.1)×10−10 for (0,4,1)...

Collisional mixing among the z3DJ and z3FJ states of Fe atoms in He and Ar

Collisional mixing among the z3DJ and z3FJ states of Fe[3d64s(a4D)4p] atoms was investigated in He and Ar by laser‐induced fluorescence method. The z3DJ and z3FJ states of Fe atoms were generated directly by photodissociation of Fe(CO)5 followed by single photon absorption within a laser pulse using an unfocussed laser beam with atomic transition frequencies of Fe. When the z3D3 level was excited, the emissions from this level showed a double exponential decay. The fast and slow components of the decay constants from the z3D3 level were 10.7×10−10 and 0.3×10−10 cm3 molecule−1 s−1 in He, and 8.8×10−10 and 1.6×10−10 cm3 molecule−1 s−1 in Ar, respectively. When the z3F4 level was pumped, the emissions from this level showed a single exponential decay and the decay constants were the same as those of the slow components of z3D3. The emissions from higher‐lying levels were single exponential at low pressures and the decay constants were in the range of 0.7–3.6×10−10 cm3 molecule−1 s−1. It is found that the col...