The infrared multiphoton dissociation(IRMPD)spectrum of the protonated heterodimer of Pro Phe H+,in the range of 2700-3700 cm^-1,has been obtained with a Fourier-transform ion cyclotron mass spectrometer combined with...The infrared multiphoton dissociation(IRMPD)spectrum of the protonated heterodimer of Pro Phe H+,in the range of 2700-3700 cm^-1,has been obtained with a Fourier-transform ion cyclotron mass spectrometer combined with an IR OPO laser.The experimental spectrum shows one peak at 3565 cm^-1 corresponding to the free carboxyl O-H stretching vibration,and two broad peaks centered at 2935 and 3195 cm^-1.Theoretical calculations were performed on the level of M062 X/6-311++G(d,p).Results show that the most stable isomer is characterized by a charge-solvated structure in which the proton is bound to the unit of proline.Its predicted spectrum is in good agreement with the experimental one,although the coexistence of salt-bridged structures cannot be entirely excluded.展开更多
The infrared multi-photon dissociation (IRMPD) of acetic anhydride to generate state- selected CH_2 has been investigated by using time and wavelength resolved fluorescence techniques. It has been observed that the ge...The infrared multi-photon dissociation (IRMPD) of acetic anhydride to generate state- selected CH_2 has been investigated by using time and wavelength resolved fluorescence techniques. It has been observed that the generation of the nascent ground state CH_2 (a^1A_1) is delayed by about 0.6 μs relative to the onset time of the excited CH_2(b^1B_1). The relative population of the ground and excited state CH_2 and the onset time for the appearance of the ground state CH_2 have been found to depend strongly on CO_2 laser output fluences. These results appear to have a strong bearing on the structure of the potential energy surfaces of the intermediate CH_2CO. A possible photolysis me- chanism is proposed to explain these experimental results.展开更多
基金supported by the National Natural Science Foundation of China(No.21627810)the Fundamental Research Funds for the Central Universities,Nankai University(No.63191523)。
文摘The infrared multiphoton dissociation(IRMPD)spectrum of the protonated heterodimer of Pro Phe H+,in the range of 2700-3700 cm^-1,has been obtained with a Fourier-transform ion cyclotron mass spectrometer combined with an IR OPO laser.The experimental spectrum shows one peak at 3565 cm^-1 corresponding to the free carboxyl O-H stretching vibration,and two broad peaks centered at 2935 and 3195 cm^-1.Theoretical calculations were performed on the level of M062 X/6-311++G(d,p).Results show that the most stable isomer is characterized by a charge-solvated structure in which the proton is bound to the unit of proline.Its predicted spectrum is in good agreement with the experimental one,although the coexistence of salt-bridged structures cannot be entirely excluded.
文摘The infrared multi-photon dissociation (IRMPD) of acetic anhydride to generate state- selected CH_2 has been investigated by using time and wavelength resolved fluorescence techniques. It has been observed that the generation of the nascent ground state CH_2 (a^1A_1) is delayed by about 0.6 μs relative to the onset time of the excited CH_2(b^1B_1). The relative population of the ground and excited state CH_2 and the onset time for the appearance of the ground state CH_2 have been found to depend strongly on CO_2 laser output fluences. These results appear to have a strong bearing on the structure of the potential energy surfaces of the intermediate CH_2CO. A possible photolysis me- chanism is proposed to explain these experimental results.
