JMS letters Received: 27 June 2013
Revised: 14 November 2013
Accepted: 16 December 2013
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/jms.3330
Mercury mono oxide cluster ions (HgO)n+ by laser desorption ionization time of flight mass spectrometry Additional supporting information may be found in the online version of this article at the publisher’s web site.
Dear Sir,
248
Mercury mono oxide (HgO) is a well-known solid, which consist of zigzag –O–Hg–O–Hg– chains with linear O–Hg–O units, and is well characterized in solid state.[1,2] However, gas phase experimental characterization of diatomic HgO is limited. The HgO molecule has been so far identified and characterized by matrix isolation infrared spectroscopy[3] and mass spectrometry.[4] In contrast to less experimental investigation, lots of theoretical quantum computational studies are available on HgO.[5–12] This is due to the significant role of HgO in the depletion of gaseous elemental mercury in the atmosphere and its subsequent deposition in the Arctic and Antarctic regions after the polar sun rise as well as its correlation with ozone depletion phenomenon.[13–15] The high temperature mass spectrometric measurements along with the thermodynamic law reported that the dissociation energy of HgO+ is 53 ± 8 kcal mol 1.[4] The measured experimental dissociation energy value of the cation contradicts the computed theoretical binding energy (4.0 kcal mol 1) of the neutral HgO molecule relative to the ground state of atoms (Hg1S0 and O3P2).[8,9] In addition, the application of relativistic effects to the nonrelativistic calculations destabilizes the molecule further.[10] An accurate ab initio electronic structure calculation by Filatov and Cremer[11,12] indicate that the dimer of mercury mono oxide (HgO)2 has two isomers: O–Hg2–O and Hg–O2–Hg, and the computed atomization energies of mercury monoxide dimmers are found to be 125 and 128 kcal mol 1, respectively, which when corrected for zero-point vibrational energies and thermal energies yield atomization energy per monomer of 59.6–60.8 kcal mol 1, which is in good in agreement with experimental dissociation energy value. Thus, they argued that the dissociation energy determined by the high temperature Knudsen cell mass spectrometry corresponds to the dissociation of (HgO)2 but not because of the dissociation of HgO into Hg and O atoms. Accordingly, the discrepancy in the experimental and calculated dissociation energy value of HgO or (HgO)2 raised question about the existence of intact HgO molecule or its clusters in gas phase. The large difference in electronegativity of χ(Hg) = 1.44 and χ(O) = 3.50 favors ionic bonding with large dipole moment (8.0 D), which allows dipole-dipole interactions between two HgO molecules and thus facilitates the formation of HgO clusters. Tossell[6] systematically explored the structures and stabilities of (HgO)n clusters using quantum chemical methods with different functional and found that the clusters of HgO are more stable for larger n values, and the stability varies when
J. Mass Spectrom. 2014, 49, 248–250
n = 2–6. He further found that one dimensional chain polymers are marginally more stable than n = 6 cluster. Thus, theoretical calculations predict the possibility HgO clusters even though the HgO monomer is theoretically predicted to be less stable. To the best of our knowledge, there is no experimental evidence available for the existence HgO or its clusters in gas phase. In this letter, we report the first observation of (HgO)n+ clusters from solid HgO using pulsed laser desorption ionization time of flight mass spectrometry (LDI-TOFMS) technique. Small quantity (few milligrams) of spectroscopic pure HgO powder (Jhonson Matthey & Co., Ltd, London) was placed over 1–2 μL of deionized water on a stainless steel surface and allowed to dry at room temperature. The air dried sample was analyzed using an indigenously developed 3-m long linear TOFMS. The resolving power of the TOFMS is found to be 600 (full width at half maximum) at 200 amu. Laser radiation with pulse energy of 20 μJ obtained from a frequency tripled Nd:YAG laser (λ = 355 nm, τ = 3 ns) was focused to ~200 μm on the sample surface. The ions generated by dissociation/desorption/ionization of solid HgO are promptly accelerated and extracted by the application of DC electric field of 20 and 10 kV, respectively. The positive ions detected by a microchannel plate detector are further amplified by a preamplifier. The signal acquired through a digital storage oscilloscope are converted into mass spectra and calibrated. Figure 1 shows the overview of the LDI mass spectrum of solid HgO. The spectral data show the formation and ionization of HgO cluster ions with different stoichiometry and abundance in the m/z range 200–20 000. The mass values are measured very accurately at the peak position; Table S1 lists the observed and calculated mass and the species corresponding to it. Analysis of the spectral data indicates the presence of (HgO)n+, Hgn+ and HgnOm+ with different stoichiometry in the plasma plume. These ions might have formed because of the fragmentation of the – Hg–O–Hg–O– chain of solid HgO resulting Hg, HgO, OHgO and O ions. We have observed mercury monoxide cluster ion (HgO) + n series up to n = 34 with almost equal abundance, and the peaks are well separated by ~216 amu, the pattern is repeated and the mass spectrum is shown in Fig. 2. Unfortunately, because of the limited resolution along with poor signal-to-noise ratio, we
* Correspondence to: T. Jayasekharan, Atomic and Molecular Physics Division, Physics Group, Bhabha Atomic Research Centre (BARC), Mumbai-400 085, India. E-mail: [email protected]
Copyright © 2014 John Wiley & Sons, Ltd.
JMS letters
Figure 1. Laser desorption ionization mass spectrum of solid HgO in the mass range m/z = 200–20 000.
could not resolve series higher than n = 34. In addition to (HgO)n+ series, two other ion series viz., Hgn+ and HgnOm+ with different stoichiometry, are also observed in the lower m/z range, and the spectra is shown in Fig. 3. In the Hgn+ series, Hg+, Hg+2 and Hg+3 show more abundance, and the abundance decreases for n > 3. The HgnOm+ ions are of two types, one with m = n x (x < n) and the other with m = n + x (x > n). The ions that belong to the former category are Hg2O+, Hg3O+, Hg3O+2 , Hg4O+, Hg4O+2 and Hg4O+3 , and these ions might have formed because of the sequential or simultaneous loss of one or more O atoms from their respective parent cluster units. Alternatively, these ions might have formed because of the reaction between Hg and O atoms during the fragmentation process. The ions formed from the latter category are Hg2O+3 and Hg3O+4 , which might have formed because of the association of O atom to their respective parent cluster units or because of the reaction between Hg and O atoms in the plasma
J. Mass Spectrom. 2014, 49, 248–250
plume. The dissociation and/or association of O atoms to the parent clusters are noted up to n = 5 of (HgO)n+ clusters. These results indicate that the (HgO)n+ cluster up to n = 5 are marginally stable and undergo fast unimolecular dissociation to form more stable Hg and/or HgnOm clusters, and from n > 5 onwards, the clusters are more stable, and no dissociation products are observed in the spectra. An asymmetry in the spectral profile is noted up to n = 5, and it ceases at higher n values, which further suggest that the Hg2O+, Hg3O+, Hg3O+2 , Hg4O+, Hg4O+2 and Hg4O+3 ions are formed from the dissociation of parent clusters rather than the direct dissociation of solid HgO. In this context, it should be noted that the ionization of molecules by photons or by electron impact is mainly governed by the Franck–Condon principle, which states that the most probable ionizing transition will be that in which the positions and momenta of the nuclei are unchanged. As a result at equilibrium geometries, the thermochemistries of neutral as well as charged species are closely similar. Hence, there may not be major differences in the thermochemistries of neutral as well as cationic (HgO)n clusters. The density functional theory along with BLYP functional show that the computed energy differences between neutral HgO unit in (HgO)n clusters are 19.2, 46.7, 59.1, 63.3 and 63.9 kcal mol 1 for (HgO)2, (HgO)3, (HgO)4, (HgO)6 and one dimensional HgO crystal, respectively.[6] The energetic value indicate that the stability of the neutral clusters increases for higher n values, and the stability remains to be the same from n = 6 onwards up to one dimensional HgO crystal. Clusters with n ≤ 5 are relatively unstable and undergo dissociation to form more stable products. This prediction is similar to the experimental observation on (HgO)n cations where HgmOn+ ions are observed for n ≤ 5. It should be noted that the gas phase HgO molecule is predicted to be unstable. However, observation of low abundance HgO+ indicate that it might have undergone dissociation resulting Hg and O atoms or polymerization leading to HgO clusters. A detailed energetic calculation on different dissociation pathways of neutral as well as ionic (HgO)n clusters provide better understanding about the stability of (HgO)n as well as other mercury oxides. The molecules such as HgH, HgH2, HHgOH and Hg(OH)2 has been identified and
Copyright © 2014 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/jms
249
Figure 2. Laser desorption ionization mass spectrum of solid HgO in the mass range m/z = 180–1800.
Figure 3. Laser desorption ionization mass spectrum of solid HgO in the mass range m/z = 1600–7400.
JMS letters characterized earlier using infrared spectroscopic method.[16–19] However, we could not resolve the HgH+, HgH2+, HHgOH+, and Hg(OH)2+ because of the limited resolution of the spectrometer, although there is a possibility of the formation of these molecules in the plasma plume because of the presence of water molecules in the sample. Further, we have not observed mass spectra corresponding to HgO+2 species indicating that the +IV oxidation state of Hg is not stable, while HgF4 is observed in matrix isolation infrared spectroscopy.[20] The increased concentration of Hg in Arctic and Antarctic regions after the polar sun rise may be attributed to the photo-induced polymerization of HgO in the atmosphere and subsequent deposition on the earth surface and in the ocean. In summary, we report the first mass spectrometric evidence for the existence of mercury monoxide cluster cations up to n = 34 using LDI technique. In addition to (HgO)n+ cluster ion series, Hgn+ and HgnOm+ with different stoichiometry is also observed in the mass spectra. The observation of Hgn+ and HgnOm+ ions in the lower m/z range may be attributed to the dissociation of (HgO)n+ clusters with n ≤ 5 and are analogous to the computed energetic of the neutral clusters. The appearance of low signal intensity HgO+ species in the spectra indicate that the molecule HgO may be marginally stable and are prompt for dissociation or polymerization reactions when exposed to light. The experimental observations of (HgO)n+ clusters will help to prepare novel cluster assembled materials and thin film devices based on HgO clusters using pulsed laser deposition method. Moreover, the ultraviolet light-induced polymerization of HgO molecule will be useful to understand the mercury cycle in the atmosphere. Yours, Thankan Jayasekharan* and Naba Kishore Sahoo Atomic and Molecular Physics Division, Physics Group, Bhabha Atomic Research Centre (BARC) Trombay, Mumbai, 400 085, India
References [1] L. Gmelin. Gmelins Handbuch der anorganischen Chemie. SystemNr. 34.Quecksilber. Springer: Berlin, 1968. [2] F. A. Cotton, G. Wilkinson, C. A. Murillo, M. Bochmann. Advanced Inorganic Chemistry, 6th ed. Wiely: New York, 1999. [3] R. Butler, S. Katz, A. Snelson, J. B. Stephens. Identification of HgO, species by matrix isolation spectroscopy. J. Phys. Chem. 1979, 83, 2578–2580. [4] M. Grade, H. Hirschwald. Energetics and stabilities of the IIB/VIAcompounds at high-temperature equilibrium conditions. Ber. Bunsen-Ges. Phys. Chem. 1982, 86, 899–907.
[5] J. A. Tossell. Calculation of the energetics for oxidation of gas-phase elemental Hg by Br and BrO. J. Phys. Chem. A 2003, 107, 7804–7808. [6] J. A. Tossell. Calculation of the energetics for the oligomerization of gas phase HgO and HgS and for the solvolysis of crystalline HgO and HgS. J. Phys. Chem. A 2006, 107, 2571–2578. [7] J. Wilcox, T. Okano. Ab initio-based mercury oxidation kinetics via bromine at post combustion flue gas condition. Energy Fuels, 2011, 25, 1348–1356. [8] B. C. Shepler, K. A. Peterson. Mercury monoxide: a systematic investigation of its ground electronic state. J. Phys. Chem. A 2003, 107, 1783–1787. [9] K. A. Peterson, B. C. Shepler, J. M. Singleton. The group 12 metal chalcogenides: an accurate multi reference configuration interaction and coupled cluster study. Mol. Phys. 2007, 105, 1139–1155. [10] S. Biering, A. Hermann, J. Furthmüller, P. Schwerdtfeger. The unusual solid-state structure of mercury oxide: relativistic density functional calculations for the group 12 oxides ZnO, CdO, and HgO. J. Phys. Chem. A, 2009, 113, 12427–12432. [11] M. Filatov, D. Cremer. Revision of the dissociation energies of mercury chalcogenides- unusual types of mercury bonding. ChemPhysChem. 2004, 5, 1547–1557. [12] D. Cremer, E. Kraka, M. Filatov. Bonding in mercury molecules described by the normalized elimination of the small component and coupled cluster theory. Chem PhysChem 2008, 9, 2510 – 2521. [13] J. Y. Lu, W. H. Schroeder, L. A. Barrie, A. Steffen, H. E. Welch, K. Martin, L. Lockhart, R. V. Hunt, G. Boila, A. Richter. Magnification of atmospheric mercury deposition to polar regions in springtime: the link to tropospheric ozone depletion chemistry. Geophys. Res. Lett. 2001, 28, 3219–3222. [14] P. A. Ariya, A. P. Dastoor, M. Amyot, W. H. Schroeder, L. Barrie, K. Anlauf, F. Raofie, A. Ryzhkov, D. Davignon, J. Lalonde. The arctic: a sink for mercury. Tellus 2004, 56 B, 397–403. [15] M. Subir, P. A. Ariya, A. P. Dastoor. A review of uncertainties in atmospheric modeling of mercury chemistry I. Uncertainties in existing kinetic parameters - fundamental limitations and the importance of heterogeneous chemistry. Atmos. Environ. 2011, 45, 5664–5676. [16] K. P. Huber, G. Herzberg. Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules. van Nostrand Reinhold: New York, 1979. [17] V. A. Macrae, T. M. Greene, A. J. Downs. Matrix studies of the thermal and photolytic reactions of Zn, Cd and Hg (M) atoms with H2O: formation and characterization of the adduct M… OH2 and photoproduct HMOH. Phys. Chem. Chem. Phys. 2004, 6, 4586–4594. [18] X. Wang, L. Andrews. Solid mercury dihydride: mercurophilic bonding in molecular HgH2 polymers, Inorg. Chem. 2004, 43, 7146–7150. [19] X. Wang, L. Andrews. Infrared spectrum of Hg(OH)2 in solid neon and argon. Inorg. Chem. 2005, 44, 108–113. [20] X. Wang, L. Andrews, S. Riedel, M. Kaupp. Mercury is a transition metal: the first experimental evidence for HgF4, Angew. Chem. Int. Ed. 2007, 46, 8371 –8375.
Supporting information Additional supporting information may be found in the online version of this article at the publisher’s web site.
250 wileyonlinelibrary.com/journal/jms
Copyright © 2014 John Wiley & Sons, Ltd.
J. Mass Spectrom. 2014, 49, 248–250
Revised: 14 November 2013
Accepted: 16 December 2013
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/jms.3330
Mercury mono oxide cluster ions (HgO)n+ by laser desorption ionization time of flight mass spectrometry Additional supporting information may be found in the online version of this article at the publisher’s web site.
Dear Sir,
248
Mercury mono oxide (HgO) is a well-known solid, which consist of zigzag –O–Hg–O–Hg– chains with linear O–Hg–O units, and is well characterized in solid state.[1,2] However, gas phase experimental characterization of diatomic HgO is limited. The HgO molecule has been so far identified and characterized by matrix isolation infrared spectroscopy[3] and mass spectrometry.[4] In contrast to less experimental investigation, lots of theoretical quantum computational studies are available on HgO.[5–12] This is due to the significant role of HgO in the depletion of gaseous elemental mercury in the atmosphere and its subsequent deposition in the Arctic and Antarctic regions after the polar sun rise as well as its correlation with ozone depletion phenomenon.[13–15] The high temperature mass spectrometric measurements along with the thermodynamic law reported that the dissociation energy of HgO+ is 53 ± 8 kcal mol 1.[4] The measured experimental dissociation energy value of the cation contradicts the computed theoretical binding energy (4.0 kcal mol 1) of the neutral HgO molecule relative to the ground state of atoms (Hg1S0 and O3P2).[8,9] In addition, the application of relativistic effects to the nonrelativistic calculations destabilizes the molecule further.[10] An accurate ab initio electronic structure calculation by Filatov and Cremer[11,12] indicate that the dimer of mercury mono oxide (HgO)2 has two isomers: O–Hg2–O and Hg–O2–Hg, and the computed atomization energies of mercury monoxide dimmers are found to be 125 and 128 kcal mol 1, respectively, which when corrected for zero-point vibrational energies and thermal energies yield atomization energy per monomer of 59.6–60.8 kcal mol 1, which is in good in agreement with experimental dissociation energy value. Thus, they argued that the dissociation energy determined by the high temperature Knudsen cell mass spectrometry corresponds to the dissociation of (HgO)2 but not because of the dissociation of HgO into Hg and O atoms. Accordingly, the discrepancy in the experimental and calculated dissociation energy value of HgO or (HgO)2 raised question about the existence of intact HgO molecule or its clusters in gas phase. The large difference in electronegativity of χ(Hg) = 1.44 and χ(O) = 3.50 favors ionic bonding with large dipole moment (8.0 D), which allows dipole-dipole interactions between two HgO molecules and thus facilitates the formation of HgO clusters. Tossell[6] systematically explored the structures and stabilities of (HgO)n clusters using quantum chemical methods with different functional and found that the clusters of HgO are more stable for larger n values, and the stability varies when
J. Mass Spectrom. 2014, 49, 248–250
n = 2–6. He further found that one dimensional chain polymers are marginally more stable than n = 6 cluster. Thus, theoretical calculations predict the possibility HgO clusters even though the HgO monomer is theoretically predicted to be less stable. To the best of our knowledge, there is no experimental evidence available for the existence HgO or its clusters in gas phase. In this letter, we report the first observation of (HgO)n+ clusters from solid HgO using pulsed laser desorption ionization time of flight mass spectrometry (LDI-TOFMS) technique. Small quantity (few milligrams) of spectroscopic pure HgO powder (Jhonson Matthey & Co., Ltd, London) was placed over 1–2 μL of deionized water on a stainless steel surface and allowed to dry at room temperature. The air dried sample was analyzed using an indigenously developed 3-m long linear TOFMS. The resolving power of the TOFMS is found to be 600 (full width at half maximum) at 200 amu. Laser radiation with pulse energy of 20 μJ obtained from a frequency tripled Nd:YAG laser (λ = 355 nm, τ = 3 ns) was focused to ~200 μm on the sample surface. The ions generated by dissociation/desorption/ionization of solid HgO are promptly accelerated and extracted by the application of DC electric field of 20 and 10 kV, respectively. The positive ions detected by a microchannel plate detector are further amplified by a preamplifier. The signal acquired through a digital storage oscilloscope are converted into mass spectra and calibrated. Figure 1 shows the overview of the LDI mass spectrum of solid HgO. The spectral data show the formation and ionization of HgO cluster ions with different stoichiometry and abundance in the m/z range 200–20 000. The mass values are measured very accurately at the peak position; Table S1 lists the observed and calculated mass and the species corresponding to it. Analysis of the spectral data indicates the presence of (HgO)n+, Hgn+ and HgnOm+ with different stoichiometry in the plasma plume. These ions might have formed because of the fragmentation of the – Hg–O–Hg–O– chain of solid HgO resulting Hg, HgO, OHgO and O ions. We have observed mercury monoxide cluster ion (HgO) + n series up to n = 34 with almost equal abundance, and the peaks are well separated by ~216 amu, the pattern is repeated and the mass spectrum is shown in Fig. 2. Unfortunately, because of the limited resolution along with poor signal-to-noise ratio, we
* Correspondence to: T. Jayasekharan, Atomic and Molecular Physics Division, Physics Group, Bhabha Atomic Research Centre (BARC), Mumbai-400 085, India. E-mail: [email protected]
Copyright © 2014 John Wiley & Sons, Ltd.
JMS letters
Figure 1. Laser desorption ionization mass spectrum of solid HgO in the mass range m/z = 200–20 000.
could not resolve series higher than n = 34. In addition to (HgO)n+ series, two other ion series viz., Hgn+ and HgnOm+ with different stoichiometry, are also observed in the lower m/z range, and the spectra is shown in Fig. 3. In the Hgn+ series, Hg+, Hg+2 and Hg+3 show more abundance, and the abundance decreases for n > 3. The HgnOm+ ions are of two types, one with m = n x (x < n) and the other with m = n + x (x > n). The ions that belong to the former category are Hg2O+, Hg3O+, Hg3O+2 , Hg4O+, Hg4O+2 and Hg4O+3 , and these ions might have formed because of the sequential or simultaneous loss of one or more O atoms from their respective parent cluster units. Alternatively, these ions might have formed because of the reaction between Hg and O atoms during the fragmentation process. The ions formed from the latter category are Hg2O+3 and Hg3O+4 , which might have formed because of the association of O atom to their respective parent cluster units or because of the reaction between Hg and O atoms in the plasma
J. Mass Spectrom. 2014, 49, 248–250
plume. The dissociation and/or association of O atoms to the parent clusters are noted up to n = 5 of (HgO)n+ clusters. These results indicate that the (HgO)n+ cluster up to n = 5 are marginally stable and undergo fast unimolecular dissociation to form more stable Hg and/or HgnOm clusters, and from n > 5 onwards, the clusters are more stable, and no dissociation products are observed in the spectra. An asymmetry in the spectral profile is noted up to n = 5, and it ceases at higher n values, which further suggest that the Hg2O+, Hg3O+, Hg3O+2 , Hg4O+, Hg4O+2 and Hg4O+3 ions are formed from the dissociation of parent clusters rather than the direct dissociation of solid HgO. In this context, it should be noted that the ionization of molecules by photons or by electron impact is mainly governed by the Franck–Condon principle, which states that the most probable ionizing transition will be that in which the positions and momenta of the nuclei are unchanged. As a result at equilibrium geometries, the thermochemistries of neutral as well as charged species are closely similar. Hence, there may not be major differences in the thermochemistries of neutral as well as cationic (HgO)n clusters. The density functional theory along with BLYP functional show that the computed energy differences between neutral HgO unit in (HgO)n clusters are 19.2, 46.7, 59.1, 63.3 and 63.9 kcal mol 1 for (HgO)2, (HgO)3, (HgO)4, (HgO)6 and one dimensional HgO crystal, respectively.[6] The energetic value indicate that the stability of the neutral clusters increases for higher n values, and the stability remains to be the same from n = 6 onwards up to one dimensional HgO crystal. Clusters with n ≤ 5 are relatively unstable and undergo dissociation to form more stable products. This prediction is similar to the experimental observation on (HgO)n cations where HgmOn+ ions are observed for n ≤ 5. It should be noted that the gas phase HgO molecule is predicted to be unstable. However, observation of low abundance HgO+ indicate that it might have undergone dissociation resulting Hg and O atoms or polymerization leading to HgO clusters. A detailed energetic calculation on different dissociation pathways of neutral as well as ionic (HgO)n clusters provide better understanding about the stability of (HgO)n as well as other mercury oxides. The molecules such as HgH, HgH2, HHgOH and Hg(OH)2 has been identified and
Copyright © 2014 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/jms
249
Figure 2. Laser desorption ionization mass spectrum of solid HgO in the mass range m/z = 180–1800.
Figure 3. Laser desorption ionization mass spectrum of solid HgO in the mass range m/z = 1600–7400.
JMS letters characterized earlier using infrared spectroscopic method.[16–19] However, we could not resolve the HgH+, HgH2+, HHgOH+, and Hg(OH)2+ because of the limited resolution of the spectrometer, although there is a possibility of the formation of these molecules in the plasma plume because of the presence of water molecules in the sample. Further, we have not observed mass spectra corresponding to HgO+2 species indicating that the +IV oxidation state of Hg is not stable, while HgF4 is observed in matrix isolation infrared spectroscopy.[20] The increased concentration of Hg in Arctic and Antarctic regions after the polar sun rise may be attributed to the photo-induced polymerization of HgO in the atmosphere and subsequent deposition on the earth surface and in the ocean. In summary, we report the first mass spectrometric evidence for the existence of mercury monoxide cluster cations up to n = 34 using LDI technique. In addition to (HgO)n+ cluster ion series, Hgn+ and HgnOm+ with different stoichiometry is also observed in the mass spectra. The observation of Hgn+ and HgnOm+ ions in the lower m/z range may be attributed to the dissociation of (HgO)n+ clusters with n ≤ 5 and are analogous to the computed energetic of the neutral clusters. The appearance of low signal intensity HgO+ species in the spectra indicate that the molecule HgO may be marginally stable and are prompt for dissociation or polymerization reactions when exposed to light. The experimental observations of (HgO)n+ clusters will help to prepare novel cluster assembled materials and thin film devices based on HgO clusters using pulsed laser deposition method. Moreover, the ultraviolet light-induced polymerization of HgO molecule will be useful to understand the mercury cycle in the atmosphere. Yours, Thankan Jayasekharan* and Naba Kishore Sahoo Atomic and Molecular Physics Division, Physics Group, Bhabha Atomic Research Centre (BARC) Trombay, Mumbai, 400 085, India
References [1] L. Gmelin. Gmelins Handbuch der anorganischen Chemie. SystemNr. 34.Quecksilber. Springer: Berlin, 1968. [2] F. A. Cotton, G. Wilkinson, C. A. Murillo, M. Bochmann. Advanced Inorganic Chemistry, 6th ed. Wiely: New York, 1999. [3] R. Butler, S. Katz, A. Snelson, J. B. Stephens. Identification of HgO, species by matrix isolation spectroscopy. J. Phys. Chem. 1979, 83, 2578–2580. [4] M. Grade, H. Hirschwald. Energetics and stabilities of the IIB/VIAcompounds at high-temperature equilibrium conditions. Ber. Bunsen-Ges. Phys. Chem. 1982, 86, 899–907.
[5] J. A. Tossell. Calculation of the energetics for oxidation of gas-phase elemental Hg by Br and BrO. J. Phys. Chem. A 2003, 107, 7804–7808. [6] J. A. Tossell. Calculation of the energetics for the oligomerization of gas phase HgO and HgS and for the solvolysis of crystalline HgO and HgS. J. Phys. Chem. A 2006, 107, 2571–2578. [7] J. Wilcox, T. Okano. Ab initio-based mercury oxidation kinetics via bromine at post combustion flue gas condition. Energy Fuels, 2011, 25, 1348–1356. [8] B. C. Shepler, K. A. Peterson. Mercury monoxide: a systematic investigation of its ground electronic state. J. Phys. Chem. A 2003, 107, 1783–1787. [9] K. A. Peterson, B. C. Shepler, J. M. Singleton. The group 12 metal chalcogenides: an accurate multi reference configuration interaction and coupled cluster study. Mol. Phys. 2007, 105, 1139–1155. [10] S. Biering, A. Hermann, J. Furthmüller, P. Schwerdtfeger. The unusual solid-state structure of mercury oxide: relativistic density functional calculations for the group 12 oxides ZnO, CdO, and HgO. J. Phys. Chem. A, 2009, 113, 12427–12432. [11] M. Filatov, D. Cremer. Revision of the dissociation energies of mercury chalcogenides- unusual types of mercury bonding. ChemPhysChem. 2004, 5, 1547–1557. [12] D. Cremer, E. Kraka, M. Filatov. Bonding in mercury molecules described by the normalized elimination of the small component and coupled cluster theory. Chem PhysChem 2008, 9, 2510 – 2521. [13] J. Y. Lu, W. H. Schroeder, L. A. Barrie, A. Steffen, H. E. Welch, K. Martin, L. Lockhart, R. V. Hunt, G. Boila, A. Richter. Magnification of atmospheric mercury deposition to polar regions in springtime: the link to tropospheric ozone depletion chemistry. Geophys. Res. Lett. 2001, 28, 3219–3222. [14] P. A. Ariya, A. P. Dastoor, M. Amyot, W. H. Schroeder, L. Barrie, K. Anlauf, F. Raofie, A. Ryzhkov, D. Davignon, J. Lalonde. The arctic: a sink for mercury. Tellus 2004, 56 B, 397–403. [15] M. Subir, P. A. Ariya, A. P. Dastoor. A review of uncertainties in atmospheric modeling of mercury chemistry I. Uncertainties in existing kinetic parameters - fundamental limitations and the importance of heterogeneous chemistry. Atmos. Environ. 2011, 45, 5664–5676. [16] K. P. Huber, G. Herzberg. Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules. van Nostrand Reinhold: New York, 1979. [17] V. A. Macrae, T. M. Greene, A. J. Downs. Matrix studies of the thermal and photolytic reactions of Zn, Cd and Hg (M) atoms with H2O: formation and characterization of the adduct M… OH2 and photoproduct HMOH. Phys. Chem. Chem. Phys. 2004, 6, 4586–4594. [18] X. Wang, L. Andrews. Solid mercury dihydride: mercurophilic bonding in molecular HgH2 polymers, Inorg. Chem. 2004, 43, 7146–7150. [19] X. Wang, L. Andrews. Infrared spectrum of Hg(OH)2 in solid neon and argon. Inorg. Chem. 2005, 44, 108–113. [20] X. Wang, L. Andrews, S. Riedel, M. Kaupp. Mercury is a transition metal: the first experimental evidence for HgF4, Angew. Chem. Int. Ed. 2007, 46, 8371 –8375.
Supporting information Additional supporting information may be found in the online version of this article at the publisher’s web site.
250 wileyonlinelibrary.com/journal/jms
Copyright © 2014 John Wiley & Sons, Ltd.
J. Mass Spectrom. 2014, 49, 248–250
