Time-Resolved FTIR Emission Spectroscopy of Transient Radicals

Abstract

Fourier Transform spectroscopy with 10 -8 second time resolution for recording IR emission spectra has been developed as an efficient means for detecting previously unknown vibrational modes of transient radicals. 193 nm photodissociation of a precursor molecule is used to generate vibrationally excited radicals, from which IR emission is recorded with time and spectral resolution. Assignment of the spectra is performed using information obtained through multiple precursors, isotopic substitution, time dependence of emission intensity, theoretical calculations, and 2-dimensional cross-spectra correlation analysis. The radicals vinyl, cyanovinyl, and OCCN have been studied with many vibrational modes identified.

Collisions of Highly Vibrationally Excited Pyrazine (Evib = 37 900 cm-1) with HOD: State-Resolved Probing of Strong and Weak Collisions

“…The dynamics of collisional energy transfer have been investigated by a number of techniques that monitor the appearance of product states. Vibrational energy gain in bath molecules has been probed using IRF 22-25 and FTIR emission. − High-resolution transient IR probing is a particularly useful approach for measuring energy gain distributions since the partitioning of exchanged energy among the vibrational, rotational, and translational degrees of freedom in the bath molecule is resolved. ,− This approach has been used for a number of donor/acceptor pairs to elucidate the dynamics of strong collisions which transfer large amounts of energy. ,− By focusing on the appearance of bath states that are not thermally populated prior to collisions with the hot donor molecule, transient absorption signals for strong collisions correspond purely to population gains due to collisional excitation. Probing strong collisions in this way is straightforward in principle but can be challenging due to the low probability of strong collisions.…”

Modulated-laser source induction system for remote detection of infrared emissions of high explosives using laser-induced thermal emission

“…Laser-Induced Thermal Emission (LITE) [1][2][3][4][5][6][7] detection of analytes is an important remote detection technique for monitoring hazardous chemicals safely. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] In a homeland security setting, the detection of high explosives (HEs) enabled by LITE spectroscopy could play an important role in maintaining safe operations while conducting real-time detection and fast analysis.…”

Rotational Spectrum of the β-Cyanovinyl Radical: A Possible Astrophysical N-Heterocycle Precursor

“…Its rotational spectrum in the centimeter and millimeter bands has been reported, 18,19 as well as its Fourier-transform infrared emission spectrum. 20,21 The β-CV radical isomers have been considered in experimental and theoretical studies of VyCN UV photodissociation 22 and in the theoretical study of the gas-phase reaction of VyCN and OH, 23 but no clear observation of these species exists.…”

“…VyCN has been studied extensively; the first rotational spectrum was published in 1959, and it has been detected in molecular clouds such as Sgr B2­(N) and TMC-1. , Of its three radical derivatives, α, cis-β, and trans-β (Figure ), only the α-cyanovinyl radical (H 2 CCCN, α-CV) has been characterized experimentally. Its rotational spectrum in the centimeter and millimeter bands has been reported, , as well as its Fourier-transform infrared emission spectrum. , The β-CV radical isomers have been considered in experimental and theoretical studies of VyCN UV photodissociation and in the theoretical study of the gas-phase reaction of VyCN and OH, but no clear observation of these species exists.…”