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Muon Radiation in Methanol: In Support of the Spur Model
Available online at www.sciencedirect.com
Physics Procedia 30 (2012) 78 – 81
12th International Conference on Muon Spin Rotation, Relaxation and Resonance
Muon Radiation in Methanol: in Support of the Spur Model Philip Cormiera, Yasuhiro Miyakeb, Khashayar Ghandia* a
Department of Chemistry Mount Allison University, Sackville, New Brunswick, Canada, E4L 2B3 b Muon Section, Material and Life Science Division, J-PARC Center, Ibaraki 319-1195, Japan
Abstract Different fractions of muon environments were studied in methanol within a temperature range of 177 K to 316 K. The diamagnetic fraction does not vary significantly with temperature, while the muonium (Mu) fraction decreases by a factor of 2 as temperature increases and the lost fraction increases with temperature at the expense of the Mu fraction It is likely that at low temperatures Mu becomes segregated from solvated electrons created in the spur leading to the increase in Mu fraction and decrease in lost fraction. As internal energy increases, the hydrogen bonding in methanol decreases. This can avoid separation of Mu from the solvated electrons in the radiolysis track increasing thus the likelihood of Mu being dephased by a solvated electron during an encounter. Our experimental data also suggests that the hot atom model is not appropriate to describe the thermalization of muons in methanol. ©©2012 organizing committee of the 2010Published Publishedby byElsevier ElsevierB.V. Ltd. Selection Selection and/or and/or peer-review peer-review under under responsibility responsibility of of the [name organizer] μsr2011 conference. Keywords: ; Methanol; Hot Atom Model; Muon; Muonium; Radiolysis; solvated electron; presolvated electron; hydrogen bonding; radiation; Spur.
1. Introduction The two competing models to describe the process of muon thermalization are the hot atom and the spur models. While Mu is a powerful probe of kinetics and local environments, the mechanism in which a muon becomes thermalized Mu has been a matter of “hot” debate [1-5].1,2,3,4,5]. Both models have the same initial stage. The initial stage is the physical stage where the muon goes through a series of scattering events and charge exchanges with a moderator, in our case the solvent methanol. This occurs on the order of tens of femto-seconds. The second stage (in the spur model) is the physicochemical stage and includes interactions of the muon with presolvated and solvated electrons, transport of the muoniated species within the radiation track and potential interactions with ionized and excited species (reactions 1-9) left in the track of muons. The physicochemical stage can occur on the *
Corresponding author. +1-506-961-0802; E-mail address:[email protected].
1875-3892 © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the organizing committee of the μsr2011 conference. doi:10.1016/j.phpro.2012.04.044
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Philip Cormier et al. / Physics Procedia 30 (2012) 78 – 81
order of ~10 fs to ~ 10 ps. In the final stage, the chemical stage, has a longer time scale of ȝs, and is less relevant to the formation of Mu [1]. In the final stage there are several “types” of muon each with its own associated fraction: Mu, PMu, diamagnetic, PD, muoniated free radicals, PR, and the lost fraction, PL, so that PMu + PD + PR + PL=1. In cases where no radicals can be formed, i.e. in saturated molecules, PR is zero [2-6]. In the hot atom model Mu is formed from the charge exchange where muonium emerges as epithermal Mu (Mu*). Mu* will then go on to either abstraction or substitution reactions that contribute to the diamagnetic fraction (PD). Those that do not go through either the abstraction or substitution reactions contribute to PMu (Mu fraction) [2]. In the spur model the muon creates groups of ionized and excited species, called spurs [3-5]. The muon thermalizes towards the end of its track and gains an electron. The fraction of each species is determined by the following competitive reactions: ȝ+*+e-ĺMu* ȝ+*+RH ĺ RHMu+* RHMu+* + RH ĺ RHMu+ + RH RHMu+ + e- ĺ Mu + RH RHMu+ + RH ĺ RMu + RH2+ Mu + esol- ĺ spin depolarized Mu Mu + R ĺ spin depolarized Mu Mu + esol- ĺ MuH + RMu + R ĺ RMu
(1) (2) (3) (4) (5) (6) (7) (8) (9)
In the outlined reaction mechanisms RH is a saturated molecule that contains an H, and R in equations 7 and 9 is any paramagnetic species resulting from the spurs other than solvated electrons. The mechanisms resulting in PMu are (1) and (4); (2), (3) and (5) contribute to the diamagnetic fraction (PD). Species that contribute to the lost fraction are: (6), (7) through spin depolarization of Mu, and (8) and (9) though ~ns diamagnetic formation from Mu [3-5]. Electric field studies have shown delayed Mu formation in several rare gases, strengthening the argument for the spur model [ 6 ]. Laser–μSR experiments also support the spur model [7]. Recently Walker et al. reported that PD shows no dependence on any physicochemical properties (including in methanol) and claimed that the hot atom theory wins over the spur model [2]. We find this study unsatisfactory as no PMu or PL was reported and no temperature effects were studied. Methanol is an ideal system to study such effects because it is available as a highly purified solvent and has a wide temperature window between its freezing point and boiling point. To test the claim of Ref. [2] regarding mechanism of Mu formation we posed the following questions: 1) Does temperature affect the different fractions in methanol? 2) Can the hot atom model explain the temperature dependence? 3) If the hot atom model fails, what radiolytic products affect the distribution of muon environments? 2. Experimental All Experiments were performed at the Japan Proton Accelerator Research Complex (J-PARC) in the Muon Science Establishment (MUSE). Beam line D1 provided surface muons with a momentum of ~29 MeV/C. The DAI-OMEGA spectrometer was used which consists of 64x2 forward and backward scintillation counters. The Transverse field coil is capable of providing a field of up to 200 G. A cryostat was modified to mount our sample with a platinum resistor for temperature readings. The temperature was controlled by use of a carrier gas (helium) to cool the sample and heating element. The methanol used was HPLC grade of 99.97% purity with a water content of 0.03%. Several rounds of
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Philip Cormier et al. / Physics Procedia 30 (2012) 78 – 81
Freeze/Pump/Thaw (FPT) were performed to remove oxygen. Samples were then placed in a stainless steel target cell, sealed and stored under nitrogen gas to avoid oxygen contamination. The initial amplitude of the environment of the muon gives the relative abundance of each species and the polarization fraction is determined by [8]: PMu=2AMu/(AS-AW) PD=(AD-AW)/(AS-AW)
(10) (11)
where AMu is the Mu amplitude, AW is the cell wall amplitude, AS is the standard amplitude and AD is the diamagnetic amplitude. We performed initial experiments at STP, to find AS in comparison with Percival et al. data [9] 3. Results and discussions We present in Fig. 1 results of the first temperature dependence study of muon fractions in liquid methanol from 177 K to below the boiling point (316 K). There is clear temperature dependence for PL and PMu, and a less dramatic dependence for PD. The hot atom model does not offer an explanation for these results as in this model the muon emerges as an epithermal muon; therefore PMu should not change with temperature. 0.25
0.50
0.21
0.40
0.19
PL
0.17
0.30
0.15 0.13
0.20
0.11 0.09
0.10
T/Viscosity (K/μPa·s)
0.23
0.07 0.00
0.05 150
200
250
300
350
Temperature/ K
Fig. 1. Left: PMu (red circles) and PD (black diamonds) decreasing with temperature. Right: PL (black diamonds) increasing with temperature; the red curve displays temperature/viscosity. Unfortunately there have been few temperature dependent studies of radiolytic yields in methanol, and early studies performed by Sargent [10] and Schlick [11] conflict with more recent findings by Getoff [12]. Nevertheless, it is generally agreed that there are three major radiolytic products from irradiating methanol at STP; the methoxy radical (CH3OÚ), H atom, and e-sol with G values of 3.75 x 10-7 mol J-1 [12], 1.57 x 10-7 mol J-1 [13] and 2 x 10-7 mol J-1 [14] respectively. We believe that there are two physical properties that influence the lost and Mu fraction; methanol’s ability to solvate electrons and the extent of hydrogen bonding, which affects diffusion in methanol. Methanol solvates electrons in a planar fashion, with the hydroxyl groups pointing at the electron in the solvent cavity [15]. Gilles et al. [16] found that the electron solvation time increases at lower temperatures to approximately 1 ns at 177 K. This suggests that at lower temperature Mu is formed from reactions 1 and 4 with presolvated electrons. In addition, the ability of methanol to hydrogen bond is inversely proportional to temperature, with the mean lifetime of a hydrogen bond being 5-7 ps at 300 K, increasing by an order of magnitude when cooled to 200 K [17]. Considering this slow change to the hydrogen bonding, the Mu near muon’s end of track becomes segregated from solvated electrons further away (from the track). As the temperature increases so does the internal energy, decreasing the hydrogen bonding in methanol. This would lead to an increased encounter rate of Mu with a solvated electron in ~ ns time scale (due to ease of diffusion), which causes dephasing of Mu spin polarization. Other paramagnetic species (CH3OÚ and H atom) resulting from the
Philip Cormier et al. / Physics Procedia 30 (2012) 78 – 81
muon track would have increased diffusion rate leading to the decrease in the Mu fraction due to depolarization on ~ns time scale. Although the lost fraction curve has different curvature from the hydrodynamic curve (fig 1.) provided in the same graph, it indicates the possibility that different species created in the spurs have different diffusion rates at different temperatures. The difference in the two curvatures could be associated with the concentration of radiolytic species varying with temperature. 4. Conclusions We have presented the first temperature dependence study of different muon fractions in methanol. We find the spur model better describes our results as the hot atom model should have no temperature dependence of PMu. According to the hot atom model one would expect at low temperatures the Mu fraction to decrease and the diamagnetic fraction to increase due to increasing density; this is not the case. Instead the spur model can appropriately describe the decrease in PMu and increase in PL at higher temperatures. This is due to an increase in diffusion rate leading to an increased encounter rate between muonium and the solvated electron and other paramagnetic species. Acknowledgements This work was financially supported by the Natural Sciences and Engineering Research Council of Canada and KEK fellowship to K. Ghandi. We thank the staff of the Material and Life Science Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) and Dr. Katsumura for use of his lab. References [1] Ghandi K, Miyake Y. Muon interactions with matter. In: Hatano Y, Katsumura Y, Mozumder A, editors. Charged particle and photon interactions with matter, New York: CRC Press; 2011, p. 196-208 [2] Walker DC, Karolczak S, Gillis HA, Porter GB, Hot model of muonium formation in liquids. Can. J. Chem. 2003;81:199-203. [3] Percival PW, Roduner E, Fischer F. Radiolysis effects in muonium chemistry. Chem. Phys. 1978;32:353-367. [4] Leung S-K, Brodovitch J-C, Percival PW, Yu D, Newman KE, The reaction of muonium with hydrated electrons. Chem. Phys. 1988;121:393-403. [5] Mogensen OG, Percival PW, Muonium formation in nonpolar liquids. Rad. Phys. Chem. 1986;28:85-89. [6] Eshchenko DG, Storchak VG, Brewer JH, Morris GD, Cottrell SP, Cox SFJ. Excess electron transport and delayed muonium formation in condensed rare gases. Physical Review B 2002;66:035105-1-16. [7] Ghandi K, Clark IP, Lord JS, Cottrell SP, Laser-muon spin spectroscopy in liquids-A technique to study the excited state chemistry of transients. PCCP 2006;9:353-359. [8] Ghandi K, Bridges MD, Arseneau DJ, Fleming DG, Muonium formation as a probe of radiation chemistry in sub- and supercritical carbon dioxide. J. Phys. Chem. A 2004;108:11613-11625. [9] Percival PW, Roduner E, Fischer F. Radiation chemistry and reaction kinetics of muonium in liquids. Adv. Chem. Ser. 1979;175:335-355. [10] Sargent FP, Gardy EM, Falle HR. Spin trapping of the primary radicals formed during radiolysis of liquid methanol. A direct study. Chem. Phys. Lett. 1974;24:120-122. [11] Schlick S, Kevan L. Spin trapping of radicals formed in gamma irradiated methanol: effect of the irradiation temperature from 77 K to 300 K. Chem. Phys. Lett. 1974;38:505-509. [12] Getoff N, Ritter A, Schwöker F, Bayer P, Primary yields of CH 3Oǜ and ǜCH2OH radicals resulting in the radiolysis of high purity methanol. Radiat. Phys. Chem.1993;41:797-801. [13] Mostafavi M, Dey GR, François L, Belloni J. Transient and stable silver clusters induced by radiolysis in methanol. J. Phys. Chem. A 2002;160:10184-10194. [14] Hentz R, Kenny-Wallace GA. The influence of molecular structure on optical absorption spectra of solvated electrons in alcohols. J. Phys. Chem. 1974;78:514-519. [15] Wishart JF. Recent Trends in Radiation Chemstry New Jersey: World Scientific Publishing Co. Pte. Ltd; 2010. [16] Gilles L, Aldrich JE, Hunt JW. Solvation time of the electron in liquid alcohols and water at room temperature. Nature Physical Science 1973;243:70-72. [17] Matsumoto M, Gubbins KE. Hydrogen bonding in liquid methanol. J. Chem. Phys. 1990;3:1981-1994.
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Physics Procedia 30 (2012) 78 – 81
12th International Conference on Muon Spin Rotation, Relaxation and Resonance
Muon Radiation in Methanol: in Support of the Spur Model Philip Cormiera, Yasuhiro Miyakeb, Khashayar Ghandia* a
Department of Chemistry Mount Allison University, Sackville, New Brunswick, Canada, E4L 2B3 b Muon Section, Material and Life Science Division, J-PARC Center, Ibaraki 319-1195, Japan
Abstract Different fractions of muon environments were studied in methanol within a temperature range of 177 K to 316 K. The diamagnetic fraction does not vary significantly with temperature, while the muonium (Mu) fraction decreases by a factor of 2 as temperature increases and the lost fraction increases with temperature at the expense of the Mu fraction It is likely that at low temperatures Mu becomes segregated from solvated electrons created in the spur leading to the increase in Mu fraction and decrease in lost fraction. As internal energy increases, the hydrogen bonding in methanol decreases. This can avoid separation of Mu from the solvated electrons in the radiolysis track increasing thus the likelihood of Mu being dephased by a solvated electron during an encounter. Our experimental data also suggests that the hot atom model is not appropriate to describe the thermalization of muons in methanol. ©©2012 organizing committee of the 2010Published Publishedby byElsevier ElsevierB.V. Ltd. Selection Selection and/or and/or peer-review peer-review under under responsibility responsibility of of the [name organizer] μsr2011 conference. Keywords: ; Methanol; Hot Atom Model; Muon; Muonium; Radiolysis; solvated electron; presolvated electron; hydrogen bonding; radiation; Spur.
1. Introduction The two competing models to describe the process of muon thermalization are the hot atom and the spur models. While Mu is a powerful probe of kinetics and local environments, the mechanism in which a muon becomes thermalized Mu has been a matter of “hot” debate [1-5].1,2,3,4,5]. Both models have the same initial stage. The initial stage is the physical stage where the muon goes through a series of scattering events and charge exchanges with a moderator, in our case the solvent methanol. This occurs on the order of tens of femto-seconds. The second stage (in the spur model) is the physicochemical stage and includes interactions of the muon with presolvated and solvated electrons, transport of the muoniated species within the radiation track and potential interactions with ionized and excited species (reactions 1-9) left in the track of muons. The physicochemical stage can occur on the *
Corresponding author. +1-506-961-0802; E-mail address:[email protected].
1875-3892 © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the organizing committee of the μsr2011 conference. doi:10.1016/j.phpro.2012.04.044
79
Philip Cormier et al. / Physics Procedia 30 (2012) 78 – 81
order of ~10 fs to ~ 10 ps. In the final stage, the chemical stage, has a longer time scale of ȝs, and is less relevant to the formation of Mu [1]. In the final stage there are several “types” of muon each with its own associated fraction: Mu, PMu, diamagnetic, PD, muoniated free radicals, PR, and the lost fraction, PL, so that PMu + PD + PR + PL=1. In cases where no radicals can be formed, i.e. in saturated molecules, PR is zero [2-6]. In the hot atom model Mu is formed from the charge exchange where muonium emerges as epithermal Mu (Mu*). Mu* will then go on to either abstraction or substitution reactions that contribute to the diamagnetic fraction (PD). Those that do not go through either the abstraction or substitution reactions contribute to PMu (Mu fraction) [2]. In the spur model the muon creates groups of ionized and excited species, called spurs [3-5]. The muon thermalizes towards the end of its track and gains an electron. The fraction of each species is determined by the following competitive reactions: ȝ+*+e-ĺMu* ȝ+*+RH ĺ RHMu+* RHMu+* + RH ĺ RHMu+ + RH RHMu+ + e- ĺ Mu + RH RHMu+ + RH ĺ RMu + RH2+ Mu + esol- ĺ spin depolarized Mu Mu + R ĺ spin depolarized Mu Mu + esol- ĺ MuH + RMu + R ĺ RMu
(1) (2) (3) (4) (5) (6) (7) (8) (9)
In the outlined reaction mechanisms RH is a saturated molecule that contains an H, and R in equations 7 and 9 is any paramagnetic species resulting from the spurs other than solvated electrons. The mechanisms resulting in PMu are (1) and (4); (2), (3) and (5) contribute to the diamagnetic fraction (PD). Species that contribute to the lost fraction are: (6), (7) through spin depolarization of Mu, and (8) and (9) though ~ns diamagnetic formation from Mu [3-5]. Electric field studies have shown delayed Mu formation in several rare gases, strengthening the argument for the spur model [ 6 ]. Laser–μSR experiments also support the spur model [7]. Recently Walker et al. reported that PD shows no dependence on any physicochemical properties (including in methanol) and claimed that the hot atom theory wins over the spur model [2]. We find this study unsatisfactory as no PMu or PL was reported and no temperature effects were studied. Methanol is an ideal system to study such effects because it is available as a highly purified solvent and has a wide temperature window between its freezing point and boiling point. To test the claim of Ref. [2] regarding mechanism of Mu formation we posed the following questions: 1) Does temperature affect the different fractions in methanol? 2) Can the hot atom model explain the temperature dependence? 3) If the hot atom model fails, what radiolytic products affect the distribution of muon environments? 2. Experimental All Experiments were performed at the Japan Proton Accelerator Research Complex (J-PARC) in the Muon Science Establishment (MUSE). Beam line D1 provided surface muons with a momentum of ~29 MeV/C. The DAI-OMEGA spectrometer was used which consists of 64x2 forward and backward scintillation counters. The Transverse field coil is capable of providing a field of up to 200 G. A cryostat was modified to mount our sample with a platinum resistor for temperature readings. The temperature was controlled by use of a carrier gas (helium) to cool the sample and heating element. The methanol used was HPLC grade of 99.97% purity with a water content of 0.03%. Several rounds of
80
Philip Cormier et al. / Physics Procedia 30 (2012) 78 – 81
Freeze/Pump/Thaw (FPT) were performed to remove oxygen. Samples were then placed in a stainless steel target cell, sealed and stored under nitrogen gas to avoid oxygen contamination. The initial amplitude of the environment of the muon gives the relative abundance of each species and the polarization fraction is determined by [8]: PMu=2AMu/(AS-AW) PD=(AD-AW)/(AS-AW)
(10) (11)
where AMu is the Mu amplitude, AW is the cell wall amplitude, AS is the standard amplitude and AD is the diamagnetic amplitude. We performed initial experiments at STP, to find AS in comparison with Percival et al. data [9] 3. Results and discussions We present in Fig. 1 results of the first temperature dependence study of muon fractions in liquid methanol from 177 K to below the boiling point (316 K). There is clear temperature dependence for PL and PMu, and a less dramatic dependence for PD. The hot atom model does not offer an explanation for these results as in this model the muon emerges as an epithermal muon; therefore PMu should not change with temperature. 0.25
0.50
0.21
0.40
0.19
PL
0.17
0.30
0.15 0.13
0.20
0.11 0.09
0.10
T/Viscosity (K/μPa·s)
0.23
0.07 0.00
0.05 150
200
250
300
350
Temperature/ K
Fig. 1. Left: PMu (red circles) and PD (black diamonds) decreasing with temperature. Right: PL (black diamonds) increasing with temperature; the red curve displays temperature/viscosity. Unfortunately there have been few temperature dependent studies of radiolytic yields in methanol, and early studies performed by Sargent [10] and Schlick [11] conflict with more recent findings by Getoff [12]. Nevertheless, it is generally agreed that there are three major radiolytic products from irradiating methanol at STP; the methoxy radical (CH3OÚ), H atom, and e-sol with G values of 3.75 x 10-7 mol J-1 [12], 1.57 x 10-7 mol J-1 [13] and 2 x 10-7 mol J-1 [14] respectively. We believe that there are two physical properties that influence the lost and Mu fraction; methanol’s ability to solvate electrons and the extent of hydrogen bonding, which affects diffusion in methanol. Methanol solvates electrons in a planar fashion, with the hydroxyl groups pointing at the electron in the solvent cavity [15]. Gilles et al. [16] found that the electron solvation time increases at lower temperatures to approximately 1 ns at 177 K. This suggests that at lower temperature Mu is formed from reactions 1 and 4 with presolvated electrons. In addition, the ability of methanol to hydrogen bond is inversely proportional to temperature, with the mean lifetime of a hydrogen bond being 5-7 ps at 300 K, increasing by an order of magnitude when cooled to 200 K [17]. Considering this slow change to the hydrogen bonding, the Mu near muon’s end of track becomes segregated from solvated electrons further away (from the track). As the temperature increases so does the internal energy, decreasing the hydrogen bonding in methanol. This would lead to an increased encounter rate of Mu with a solvated electron in ~ ns time scale (due to ease of diffusion), which causes dephasing of Mu spin polarization. Other paramagnetic species (CH3OÚ and H atom) resulting from the
Philip Cormier et al. / Physics Procedia 30 (2012) 78 – 81
muon track would have increased diffusion rate leading to the decrease in the Mu fraction due to depolarization on ~ns time scale. Although the lost fraction curve has different curvature from the hydrodynamic curve (fig 1.) provided in the same graph, it indicates the possibility that different species created in the spurs have different diffusion rates at different temperatures. The difference in the two curvatures could be associated with the concentration of radiolytic species varying with temperature. 4. Conclusions We have presented the first temperature dependence study of different muon fractions in methanol. We find the spur model better describes our results as the hot atom model should have no temperature dependence of PMu. According to the hot atom model one would expect at low temperatures the Mu fraction to decrease and the diamagnetic fraction to increase due to increasing density; this is not the case. Instead the spur model can appropriately describe the decrease in PMu and increase in PL at higher temperatures. This is due to an increase in diffusion rate leading to an increased encounter rate between muonium and the solvated electron and other paramagnetic species. Acknowledgements This work was financially supported by the Natural Sciences and Engineering Research Council of Canada and KEK fellowship to K. Ghandi. We thank the staff of the Material and Life Science Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) and Dr. Katsumura for use of his lab. References [1] Ghandi K, Miyake Y. Muon interactions with matter. In: Hatano Y, Katsumura Y, Mozumder A, editors. Charged particle and photon interactions with matter, New York: CRC Press; 2011, p. 196-208 [2] Walker DC, Karolczak S, Gillis HA, Porter GB, Hot model of muonium formation in liquids. Can. J. Chem. 2003;81:199-203. [3] Percival PW, Roduner E, Fischer F. Radiolysis effects in muonium chemistry. Chem. Phys. 1978;32:353-367. [4] Leung S-K, Brodovitch J-C, Percival PW, Yu D, Newman KE, The reaction of muonium with hydrated electrons. Chem. Phys. 1988;121:393-403. [5] Mogensen OG, Percival PW, Muonium formation in nonpolar liquids. Rad. Phys. Chem. 1986;28:85-89. [6] Eshchenko DG, Storchak VG, Brewer JH, Morris GD, Cottrell SP, Cox SFJ. Excess electron transport and delayed muonium formation in condensed rare gases. Physical Review B 2002;66:035105-1-16. [7] Ghandi K, Clark IP, Lord JS, Cottrell SP, Laser-muon spin spectroscopy in liquids-A technique to study the excited state chemistry of transients. PCCP 2006;9:353-359. [8] Ghandi K, Bridges MD, Arseneau DJ, Fleming DG, Muonium formation as a probe of radiation chemistry in sub- and supercritical carbon dioxide. J. Phys. Chem. A 2004;108:11613-11625. [9] Percival PW, Roduner E, Fischer F. Radiation chemistry and reaction kinetics of muonium in liquids. Adv. Chem. Ser. 1979;175:335-355. [10] Sargent FP, Gardy EM, Falle HR. Spin trapping of the primary radicals formed during radiolysis of liquid methanol. A direct study. Chem. Phys. Lett. 1974;24:120-122. [11] Schlick S, Kevan L. Spin trapping of radicals formed in gamma irradiated methanol: effect of the irradiation temperature from 77 K to 300 K. Chem. Phys. Lett. 1974;38:505-509. [12] Getoff N, Ritter A, Schwöker F, Bayer P, Primary yields of CH 3Oǜ and ǜCH2OH radicals resulting in the radiolysis of high purity methanol. Radiat. Phys. Chem.1993;41:797-801. [13] Mostafavi M, Dey GR, François L, Belloni J. Transient and stable silver clusters induced by radiolysis in methanol. J. Phys. Chem. A 2002;160:10184-10194. [14] Hentz R, Kenny-Wallace GA. The influence of molecular structure on optical absorption spectra of solvated electrons in alcohols. J. Phys. Chem. 1974;78:514-519. [15] Wishart JF. Recent Trends in Radiation Chemstry New Jersey: World Scientific Publishing Co. Pte. Ltd; 2010. [16] Gilles L, Aldrich JE, Hunt JW. Solvation time of the electron in liquid alcohols and water at room temperature. Nature Physical Science 1973;243:70-72. [17] Matsumoto M, Gubbins KE. Hydrogen bonding in liquid methanol. J. Chem. Phys. 1990;3:1981-1994.
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