Rotational energy transfer within CH A 2Δ(v=0) and B 2Σ−(v=0) states by collisions with He, Ar, N2, CO, N2O, and CHBr3 using a time-resolved Fourier transform spectrometer

Abstract

By using a step-scan Fourier transform spectrometer, we have studied collisionally-induced rotational energy transfer (RET) of the CH A(2Δ) (N⩽16,v=0) and B(2Σ−) (N⩽16,v=0) states. The collision partners used for the B state are He, Ar, N2, CO, N2O, and CHBr3, while He and Ar are for the A state. The time-resolved spectra obtained in the nanosecond regime may yield the RET information straightforward under a single pressure of the collider. The resultant RET rate constants for both states range from 10−12 to 10−10 cm3 molecule−1 s−1, comparable to the gas kinetic. The trend follows the order of He∼Ar<N2∼CO<N2O<CHBr3 for the B state, and He<Ar for the A state. For the B state, the findings of multi-quantum changing collisions up to ΔN=±3 and markedly large rate constants imply that the RET collisions are dominated by long-range attractive force. The collision complexes possibly formed between the CH(B) and the colliders are long-lived enough to allow for effective removal of the rotational energy more than a quantum level in a single collision. In contrast, a single quantum change in the RET collision found in the A state suggests dominance of a repulsive interaction between the colliding species, which has been verified previously in the measurements of temperature dependence of the electronic quenching.

Photodissociation of Gaseous Acetyl Chloride at 248 nm by Time-Resolved Fourier-Transform Infrared Spectroscopy: The HCl, CO, and CH2 Product Channels

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Fourier Transform Near-Infrared Absorption Spectroscopic Study of Catalytic Isomerization of Quadricyclane to Norbornadiene by Copper(II) and Tin(II) Salts

“…A step-scan Fourier transform spectrometer (FTS, IFS-88, Bruker) was implemented with a tungsten lamp as the NIR radiation source and a Si diode detector available for the wavelength range from 6000 to 25000 cm -1 . The FTS contains a classical Michelson interferometer, which can be operated in either rapid-scan or step-scan mode. − In this work a rapid-scan mode was used. The obtained interferogram in each scan, as completed within milliseconds, was Fourier transformed and displayed.…”

Photodissociation of gaseous CH3COSH at 248 nm by time-resolved Fourier-transform infrared emission spectroscopy: Observation of three dissociation channels

“…The FTIR was performed in a step-scan mode, with which the movable mirror of the interferometer can be moved stepby-step. [30][31][32][33] In this work the digitized signals which were repeatedly collected for 30 laser shots were monitored with an InSb detector cooled at 77 K, followed by a preamplifier. The detector and preamplifier had the response time of ∼700 and ∼200 ns, respectively.…”