Mode-Selective Vibrational Energy Transfer Dynamics in 1,3,5-Trinitroperhydro-1,3,5-Triazine (RDX) Thin Films

2021 ◽  
Author(s):  
Neil Cole-Filipiak ◽  
Robert Knepper ◽  
Mitchell A. Wood ◽  
Krupa Ramasesha
Keyword(s):  
Energy Transfer ◽  
Thermal Equilibrium ◽  
Transient Absorption ◽  
Vibrational Energy ◽  
Energetic Material ◽  
Transient Absorption Spectroscopy ◽  
Vibrational Energy Transfer ◽  
Mid Infrared ◽  
Mode Selectivity ◽  
Anharmonic Coupling

Herein, we report on the sub-picosecond to sub-nanosecond vibrational energy transfer (VET) dynamics of the solid energetic material 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) using broadband, ultrafast infrared transient absorption spectroscopy. Experiments reveal VET occurring on three distinct timescales: sub-picosecond, 5 ps, and 200 ps. The ultrafast appearance of signal at all probed modes in the mid-infrared suggests strong anharmonic coupling of all vibrations in the solid whereas the long-lived evolution demonstrates that VET is incomplete, and thus thermal equilibrium is not attained, even on the hundred picosecond timescale. Mode-selectivity of the longest dynamics suggests coupling of the N–N and axial NO<sub>2</sub> stretching modes with the long-lived, excited phonon bath.

scholarly journals Mode-Selective Vibrational Energy Transfer Dynamics in 1,3,5-Trinitroperhydro-1,3,5-Triazine (RDX) Thin Films

2021 ◽  
Author(s):  
Neil Cole-Filipiak ◽  
Robert Knepper ◽  
Mitchell A. Wood ◽  
Krupa Ramasesha
Keyword(s):  
Energy Transfer ◽  
Thermal Equilibrium ◽  
Transient Absorption ◽  
Vibrational Energy ◽  
Energetic Material ◽  
Transient Absorption Spectroscopy ◽  
Vibrational Energy Transfer ◽  
Mid Infrared ◽  
Mode Selectivity ◽  
Anharmonic Coupling

Herein, we report on the sub-picosecond to sub-nanosecond vibrational energy transfer (VET) dynamics of the solid energetic material 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) using broadband, ultrafast infrared transient absorption spectroscopy. Experiments reveal VET occurring on three distinct timescales: sub-picosecond, 5 ps, and 200 ps. The ultrafast appearance of signal at all probed modes in the mid-infrared suggests strong anharmonic coupling of all vibrations in the solid whereas the long-lived evolution demonstrates that VET is incomplete, and thus thermal equilibrium is not attained, even on the hundred picosecond timescale. Mode-selectivity of the longest dynamics suggests coupling of the N–N and axial NO<sub>2</sub> stretching modes with the long-lived, excited phonon bath.

Vibrational Energy Transfer in High Explosives: Nitromethane

1995 ◽  
Vol 418 ◽  
Author(s):  
Xiaoyu Hong ◽  
Jeffrey R. Hill ◽  
Dana D. Dlott
Keyword(s):  
Energy Transfer ◽  
Energetic Materials ◽  
Vibrational Energy ◽  
High Explosive ◽  
Vibrational Energy Transfer ◽  
Ambient Conditions ◽  
High Explosives ◽  
Time Resolved ◽  
Mid Infrared ◽  
Shock Initiation

AbstractTime resolved vibrational spectroscopy with picosecond tunable mid-infrared pulses is used to measure the rates and investigate the detailed mechanisms of multiphonon up-pumping and vibrational cooling in a condensed high explosive, nitromethane. Both processes occur on the ˜100 ps time scale under ambient conditions. The mechanisms involve sequential climbing or descending the ladder of molecular vibrations. Efficient intermolecular vibrational energy transfer from various molecules to the symmetric stretching excitation of NO2 is observed. The implications of these measurements for understanding shock initiation to detonation and the sensitivities of energetic materials to shock initiation are discussed briefly.

Thymine Dimerization Induced by Oxidative DNA Lesions and Epigenetic Intermediates via Triplet-Triplet Energy Transfer

2020 ◽  
Author(s):  
Mauricio Lineros-Rosa ◽  
Antonio Francés-Monerris ◽  
Antonio Monari ◽  
Miguel Angél Miranda ◽  
Virginie Lhiaubet-Vallet
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Dna Lesions ◽  
Transient Absorption Spectroscopy ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Dna Nucleobases

Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidative lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer the excitation energy to thymine-thymine dyads, inducing the formation of the highly toxic and mutagenic cyclobutane pyrimidine dimers (CPDs). By using steady-state and transient absorption spectroscopy, NMR, HPLC, and theoretical calculations, we quantify the differences in the triplet-triplet energy transfer mediated by ForU and ForC, revealing that the former is much more efficient in delivering the excitation energy and producing the CPD photoproduct. Although significantly slower than ForU, ForC is also able to harm DNA nucleobases and therefore this process has to be taken into account as a viable photosensitization mechanism. The present findings evidence a rich photochemistry crucial to understand DNA photodamage and of potential use in the development of biomarkers and non-conventional photodynamic therapy agents.

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