Internal energy of product ions formed in mass spectral reactions. Degrees of freedom effect

Bente, P. F.; McLafferty, Fred W.; McAdoo, David J.; Lifshitz, Chava

doi:10.1021/j100574a011

Cited by 45 publications

(18 citation statements)

References 8 publications

(10 reference statements)

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“…This field abruptly shifts the position of hydrogen atoms without changing the Hamiltonian of the diatomic dipoles, which is assumed to be an oscillator system. Thus, the probability function P tr is given by (10) The parameter a in (10) is the value of the shift, which can be calculated in the frame of the presented model by (11) where F is the vector of the electric field and m is the mass of the diatomic group (i). …”

Section: Accumulation Of Excimolsmentioning

confidence: 99%

“…The main parts of the presented theoretical model were proven by analysing some experimental results presented in [4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…

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mentioning

confidence: 99%

“…Also, it was shown that IR photon induced dissociation (IR-PID) leads with high probability to fragments consisting of small atomic groups. These groups are mainly the end groups of the chain-like substructures inside the irradiated molecules [6][7][8][9][10][11][12]. The abundance of different fragments depends on the photon fluence, on the number of diatomic groups in the chains and on the corresponding dissociation energies [6][7][8][9][10][11][12].…”

mentioning

confidence: 99%

“…These groups are mainly the end groups of the chain-like substructures inside the irradiated molecules [6][7][8][9][10][11][12]. The abundance of different fragments depends on the photon fluence, on the number of diatomic groups in the chains and on the corresponding dissociation energies [6][7][8][9][10][11][12].In the present work a model for the dissociation of organic molecules with chain-like substructures by IR-PID is suggested. The model is based on the excimol theory for excitation and fragmentation of organic molecules, which was worked out previously [13].…”

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confidence: 99%

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Resonant IR Photon Induced Dissociation in Organic Molecules with Chain-like Substructures

Jungclas

Schmidt

Komarov

et al. 2002

Zeitschrift Für Naturforschung A

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IntroductionPhoton induced dissociation (PID) of molecules due to action of low intensity IR radiation is the subject of several experimental investigations [1][2][3][4][5][6][7][8][9][10][11][12]. The interest in this field arose, as information of molecular dissociation by IR photons is important not only for the development of quantum chemistry of organic molecules and for the theory of laser beam interactions with large molecules, but also for practical applications. It was shown experimentally that the PID of molecules consisting of chain-like substructures can be induced resonantly by IR radiation with frequencies which do not coincide with the vibrational frequencies of the diatomic valence groups contained in these molecules [4,5]. Also, it was shown that IR photon induced dissociation (IR-PID) leads with high probability to fragments consisting of small atomic groups. These groups are mainly the end groups of the chain-like substructures inside the irradiated molecules [6][7][8][9][10][11][12]. The abundance of different fragments depends on the photon fluence, on the number of diatomic groups in the chains and on the corresponding dissociation energies [6][7][8][9][10][11][12].In the present work a model for the dissociation of organic molecules with chain-like substructures by IR-PID is suggested. The model is based on the excimol theory for excitation and fragmentation of organic molecules, which was worked out previously [13]. In the frame of the excimol theory the collection of internal molecular energy occurs in chain-like molecular substructures consisting of identical diatomic groups with significant dipole momenta. In these chains many collective vibrational states (excimols) with frequency w ex are induced by a resonant external periodic field, e.g. IR photons. The excimol energy E ex = h w ex is less than the energy E 01 = h w 01 of the first vibrational state of an isolated diatomic quantum oscillator. This energy difference is caused by the energy E tr required for energy transitions within the chain from one diatomic oscillator to another. These tansitions are due to resonance dipole-dipole interactions between identical molecular dipoles and the transition energy E tr which strongly depends on the dipole moment of the diatomic groups and on the three-dimensional structure of the chain [14,15]. The excimol lifetime t ex is larger than the lifetime t 01 of the excitation of an isolated diatomic oscillator in the first vibrational state, because the resonance interaction of the diatomic dipoles within the chain decreases the probability of vibrational relaxation in each dipole. For example, the excimol lifetime t ex in a (CH 2 ) n chain is two orders of magnitude higher than the lifetime t 01 of the excitation of an isolated CH-group.Resonant excimol excitation can be induced by periodic electromagnetic fields including IR-fields, if the frequency of the field is equal to the excimol frequency. Several excimols can be excited independently in a chain. They are not accumulated in a single diat...

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Section: Accumulation Of Excimolsmentioning

confidence: 99%

“…The main parts of the presented theoretical model were proven by analysing some experimental results presented in [4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…

…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Resonant IR Photon Induced Dissociation in Organic Molecules with Chain-like Substructures

Jungclas

Schmidt

Komarov

et al. 2002

Zeitschrift Für Naturforschung A

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ChemInform Abstract: METASTABLE ION CHARACTERISTICS PART 32, INTERNAL ENERGY OF PRODUCT IONS FORMED IN MASS SPECTRAL REACTIONS, THE DEGREES OF FREEDOM EFFECT

Bente¹,

McLafferty²,

McAdoo³

et al. 1975

Chemischer Informationsdienst

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MassKinetics: a theoretical model of mass spectra incorporating physical processes, reaction kinetics and mathematical descriptions

2001

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A theoretical framework and an accompanying computer program (MassKinetics, www.chemres.hu/ms/ masskinetics) is developed for describing reaction kinetics under statistical, but non-equilibrium, conditions, i.e. those applying to mass spectrometry. In this model all the important physical processes influencing product distributions are considered: reactions, including the effects of acceleration, collisions and photon exchange. These processes occur simultaneously and are taken into account by the master equation approach. The system is described by (independent) product, kinetic energy and internal energy distributions, and the time development of these distributions is studied using transition probability functions. The product distribution at the end of the experiment corresponds to the mass spectrum. Individual elements in this scheme are mostly well known: internal energy-dependent reaction rates are calculated by transition state theory (RRK or RRKM formalisms). In the course of collisions, energy transfer and other processes may occur (the latter usually resulting in the 'loss' of ion signal). Collisions are characterized by their probability and by energy transfer in a single collision. To describe single collisions, three collision models are used: long-lived collision complexes, partially inelastic collisions and partially inelastic collisions with cooling. The latter type has been developed here, and is capable of accounting for cooling effects occurring in collision cascades. Descriptions of photon absorption and emission are well known in principle, and these are also taken into account, in addition to changes in kinetic energy due to external (electric) fields. These changes in the system occur simultaneously, and are described by master equations (a set of differential equations). The usual form of the master equation (taking into account reactions and collisional excitation) was extended to consider also radiative energy transfer, kinetic energy changes, energy partitioning and ion loss collisions. Initial results show that close to experimental accuracy can be obtained with MassKinetics, using few or no adjustable parameters. The model/program can be used to model almost all types of mass spectrometric experiments (e.g. MIKE, CID, SORI and resonant excitation). Note that it was designed for mass spectrometric applications, but can also be used to study reaction kinetics in other non-equilibrium systems.

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Internal energy of product ions formed in mass spectral reactions. Degrees of freedom effect

Cited by 45 publications

References 8 publications

Resonant IR Photon Induced Dissociation in Organic Molecules with Chain-like Substructures

Resonant IR Photon Induced Dissociation in Organic Molecules with Chain-like Substructures

ChemInform Abstract: METASTABLE ION CHARACTERISTICS PART 32, INTERNAL ENERGY OF PRODUCT IONS FORMED IN MASS SPECTRAL REACTIONS, THE DEGREES OF FREEDOM EFFECT

MassKinetics: a theoretical model of mass spectra incorporating physical processes, reaction kinetics and mathematical descriptions

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