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•The product state distributions in trimethylamine photodissociation were measured.•The CH3 photofragments showed dual ring-like scattering distributions.•The slow CH3 fragment was ...ascribed to the production of the excited state N(CH3)2.•The energy threshold of CN fission was located between the S2 and S1 state origins.
The photodissociation dynamics of trimethylamine, N(CH3)3, was studied using ion-imaging. The photolysis wavelength was scanned over the 200–236 nm region, where the S1(3s) and S2(3p) states were excited with varying relative populations. The dissociation threshold of CN bond fission was found at 42,500 cm−1, which is located between the S1(3s) and S2(3p) origins. The final-state distributions were qualitatively insensitive to the photoinitiated states, indicating a dissociation mechanism following ultrafast electronic dynamics. The CH3 photofragments showed dual ring-like scattering distributions, which were ascribed to branching to the CH3 + N(CH3)2 (A∼2A1) and CH3 + N(CH3)2 (X∼2B1) pathways.
Ion-imaging and dispersed fluorescence spectroscopy are employed for the photodissociation dynamics study of methylamine in the photolysis wavelength range 205–213 nm. The methyl radical product is ...found to populate a wide range of ro-vibrational states, among which the CH3 fragment generated in the v = 0 state shows a bimodal kinetic energy distribution. The internal energy analysis of the NH2 counterproduct indicates that a lower kinetic energy component, which was observed only with the CH3(v=0) fragment, energetically matches the electronically excited Ã2A1 state. The dispersed fluorescence spectrum, whose band structure is assigned to the Ã2A1 → X̃2B1 transition, provides evidence of the CH3(v=0) + NH2(Ã2A1) pathway. The branching mechanism of the product pathway is discussed in terms of nuclear dynamics in the long-range region, where the conical intersection between the excited- and ground-state potential energy surfaces can play a significant role.
An apparatus has been developed for electron-atom Compton scattering experiments that can employ a pulsed laser and a picosecond pulsed electron beam in a pump-and-probe scheme. The design and ...technical details of the apparatus are described. Furthermore, experimental results on the Xe atom in its ground state are presented to illustrate the performance of the pulsed electron gun and the detection and spectrometric capabilities for scattered electrons. The scope of future application is also discussed, involving real-time measurement of intramolecular force acting on each constituent atom with different mass numbers, in a transient, evolving system during a molecular reaction.
Ion-imaging and dispersed fluorescence spectroscopy are employed for the photodissociation dynamics study of methylamine in the photolysis wavelength range 205-213 nm. The methyl radical product is ...found to populate a wide range of ro-vibrational states, among which the CH
fragment generated in the v = 0 state shows a bimodal kinetic energy distribution. The internal energy analysis of the NH
counterproduct indicates that a lower kinetic energy component, which was observed only with the CH
(v=0) fragment, energetically matches the electronically excited Ã
A
state. The dispersed fluorescence spectrum, whose band structure is assigned to the Ã
A
→ X̃
B
transition, provides evidence of the CH
(v=0) + NH
(Ã
A
) pathway. The branching mechanism of the product pathway is discussed in terms of nuclear dynamics in the long-range region, where the conical intersection between the excited- and ground-state potential energy surfaces can play a significant role.
The nonradiative decay pathways of jet-cooled para-methoxy methylcinnamate (p-MMC) and para-methoxy ethylcinnamate (p-MEC) have been investigated by picosecond pump–probe and nanosecond UV-Deep UV ...pump–probe spectroscopy. The possible relaxation pathways were calculated by the (time-dependent) density functional theory. We found that p-MMC and p-MEC at low excess energy undergo multistep intersystem crossing (ISC) from the bright S1 (1 ππ*) state to the lowest triplet T1 (3 ππ*) state via two competing pathways through the T2 state in the time scale of 100 ps: (a) stepwise ISC followed after the internal conversion (IC) from S1 to the dark 1nπ* state; (b) direct ISC from the S1 to T2 states. These picosecond multistep ISCs result in the torsion of CC double bond by ∼95° in the T1 state, whose measured adiabatic energy and lifetime are 16577 cm–1 and ∼20 ns, respectively, for p-MMC. These results suggest that the ISC processes play an indispensable role in the photoprotecting sunscreens in natural plants.
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•Significant participation of the higher-order terms in the highly rotationally excited states.•Generation of the highly rotationally excited states by the reaction ...dynamics.•Determination of the sextet-order centrifugal distortion constants of NO.•Refinement of the band origins of the A–X transition of NO.•Decay of the highly rotationally excited states at a single collision level in a cell.
The highly rotationally excited states in the A2Σ+-X2ΠΩ band of NO were investigated by laser-induced fluorescence and multi-photon ionization spectroscopy. The rotational states with J up to 80.5 were prepared by CH3ONO photodissociation in the S1 and S2 excited states for spectroscopic measurements. In total, 3890 lines of nine vibronic bands were analyzed. The observed line positions deviated from the values calculated using the previous molecular constants as J increased in the J > 50.5 region. The sextet-order centrifugal distortion constants were determined for the A2Σ+and X2ΠΩ states so that the transition frequencies associated with the high-J states could reproduce the observed results within the experimental accuracy. The band origin values, whose errors have been discussed in previous studies, were refined in the present analysis. The experimental condition to suppress the rotational relaxation of the high-J states was examined, enabling us to determine the higher-order centrifugal distortion constants.
•The Chattonella antiqua blooms initially formed in the northern area of the Yatsushiro Sea.•The blooms were triggered in the riverine water advection in the southern area.•The southward advection ...was determined by the wind stress and pressure gradient.
The dynamics of river plume in relation to harmful blooms of the raphidophycean flagellate, Chattonella antiqua in summer 2008–2010 in the Yatsushiro Sea, Japan were studied using a hydrodynamic model and monitoring data. In the southern area, the bloom formed in the waters stratified by a halocline caused by the southward expansion of riverine water from the Kuma River after the bloom initially forming in the northern area. The timing of the southward riverine water advection can be explained by the balance between the wind stress term and the pressure gradient term calculated from the horizontal density difference between the northern and southern areas. The wind stress and pressure gradient terms were evaluated using the sea surface temperature, salinity, wind speed and direction at two stations. Real time monitoring or continuous observations in these areas will enable nowcasts of bloom expansion when a bloom develops in the northern area.
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