“…Although the low absolute signal magnitude prohibits any higher resolution of the emission spectrum than that achieved, we are satisfied that the blue, green, red, and IR emissions which we observe are from MnCl* in the e 5 Σ + −a 5 Σ + , d 5 Π−a 5 Σ + /X 7 Σ + , c 5 Σ + −a 5 Σ + , and b 5 Π−a 5 Σ + band systems, respectively. There are no known Mn atomic transitions 7,25,30 which could be accessed with the observed initial thresholds; the different collision energy dependences in the different regions (and the absence of UV emission) exclude SiCl 2 *; , and no electronic absorptions of MnCl 2 are known below 250 nm, , despite the undoubted presence of manganese dihalide species in many of the monohalide spectroscopic investigations. − Since the ground state of MnCl 2 must be a sextet (Mn 2+ ...3d 5 ), any dihalide emission bands in the visible region would have to involve quartet excited states, which would be expected to be highly excited as the symmetric d-electron configuration would be broken. The initial line-of-centers dependence also indicates a monohalide product; formation of MnCl 2 * would imply a much less direct interaction, with the initial collision energy dependence expected to follow eq 3 with n > 1.…”
Section: Discussionmentioning
confidence: 99%
“…Of those shown in the figure, only the UV system had been definitely assigned, as A 7 Π → X 7 Σ + (a far-UV system not shown on the figure, and designated B 7 Σ + → X 7 Σ + , had also been detected for MnF and MnCl , ). For the rest, analysis of the vibrational, and in some cases rotational, structure had allowed a number of vibrational constants, ν 00 values, and probable term symbols of the participating state pairs to be deduced, but neither the exact identity of the lower state of the transition nor its excitation energy was known. 1 Schematic representation of the electronic spectroscopy of the Mn monohalides, MnX, ,− as known at the time of our recent Mn + SnCl 4 report . The MnCl bands marked ?…”
Section: Introductionmentioning
confidence: 99%
“…Schematic representation of the electronic spectroscopy of the Mn monohalides, MnX, ,− as known at the time of our recent Mn + SnCl 4 report . The MnCl bands marked ?…”
Chemiluminescence in four different MnCl band systems
e5Σ+ → a5Σ+
(“blue”), d5Π → a5Σ+
(“green”),
c5Σ+ → a5Σ+
(“red”), and b5Π → a5Σ+
(“infrared”) has been observed from the interaction of a
laser-ablated beam of Mn atoms with gaseous SiCl4. The
initial translational thresholds range from ∼150 to
∼300
kJ mol-1, increasing in the order
e5Σ+ < c5Σ+
∼ d5Π < b5Π. Analysis of the
measured excitation functions,
in terms of a multiple line-of-centers model [Levy, M. R.
Res. Chem. Kinetics
1993,
1, 163], shows that, with
the exception of a high-energy c5Σ+ channel
contribution to d5Π production and possibly a joint
c5Σ+/d5Π
production process at low energies, all the reactions take place on
distinct potential surfaces. Although, on
energetic grounds, the b5Π and
c5Σ+ channels could derive from reaction of
ground-state Mn(a6S) atoms, the
first excited state, a6DJ, is the most likely
reagent species in all cases, indicating substantial excess
barriers.
In contrast to the corresponding SnCl4 reactions, only
the c5Σ+ excitation function reveals a
shift forward in
transition-state location with increasing collision energy. The
results have been rationalized in terms of a
hierarchy of ionic−covalent curve crossings at short internuclear
distances.
“…Although the low absolute signal magnitude prohibits any higher resolution of the emission spectrum than that achieved, we are satisfied that the blue, green, red, and IR emissions which we observe are from MnCl* in the e 5 Σ + −a 5 Σ + , d 5 Π−a 5 Σ + /X 7 Σ + , c 5 Σ + −a 5 Σ + , and b 5 Π−a 5 Σ + band systems, respectively. There are no known Mn atomic transitions 7,25,30 which could be accessed with the observed initial thresholds; the different collision energy dependences in the different regions (and the absence of UV emission) exclude SiCl 2 *; , and no electronic absorptions of MnCl 2 are known below 250 nm, , despite the undoubted presence of manganese dihalide species in many of the monohalide spectroscopic investigations. − Since the ground state of MnCl 2 must be a sextet (Mn 2+ ...3d 5 ), any dihalide emission bands in the visible region would have to involve quartet excited states, which would be expected to be highly excited as the symmetric d-electron configuration would be broken. The initial line-of-centers dependence also indicates a monohalide product; formation of MnCl 2 * would imply a much less direct interaction, with the initial collision energy dependence expected to follow eq 3 with n > 1.…”
Section: Discussionmentioning
confidence: 99%
“…Of those shown in the figure, only the UV system had been definitely assigned, as A 7 Π → X 7 Σ + (a far-UV system not shown on the figure, and designated B 7 Σ + → X 7 Σ + , had also been detected for MnF and MnCl , ). For the rest, analysis of the vibrational, and in some cases rotational, structure had allowed a number of vibrational constants, ν 00 values, and probable term symbols of the participating state pairs to be deduced, but neither the exact identity of the lower state of the transition nor its excitation energy was known. 1 Schematic representation of the electronic spectroscopy of the Mn monohalides, MnX, ,− as known at the time of our recent Mn + SnCl 4 report . The MnCl bands marked ?…”
Section: Introductionmentioning
confidence: 99%
“…Schematic representation of the electronic spectroscopy of the Mn monohalides, MnX, ,− as known at the time of our recent Mn + SnCl 4 report . The MnCl bands marked ?…”
Chemiluminescence in four different MnCl band systems
e5Σ+ → a5Σ+
(“blue”), d5Π → a5Σ+
(“green”),
c5Σ+ → a5Σ+
(“red”), and b5Π → a5Σ+
(“infrared”) has been observed from the interaction of a
laser-ablated beam of Mn atoms with gaseous SiCl4. The
initial translational thresholds range from ∼150 to
∼300
kJ mol-1, increasing in the order
e5Σ+ < c5Σ+
∼ d5Π < b5Π. Analysis of the
measured excitation functions,
in terms of a multiple line-of-centers model [Levy, M. R.
Res. Chem. Kinetics
1993,
1, 163], shows that, with
the exception of a high-energy c5Σ+ channel
contribution to d5Π production and possibly a joint
c5Σ+/d5Π
production process at low energies, all the reactions take place on
distinct potential surfaces. Although, on
energetic grounds, the b5Π and
c5Σ+ channels could derive from reaction of
ground-state Mn(a6S) atoms, the
first excited state, a6DJ, is the most likely
reagent species in all cases, indicating substantial excess
barriers.
In contrast to the corresponding SnCl4 reactions, only
the c5Σ+ excitation function reveals a
shift forward in
transition-state location with increasing collision energy. The
results have been rationalized in terms of a
hierarchy of ionic−covalent curve crossings at short internuclear
distances.
“…Launila and Simard have referred to, but apparently not yet published, high-resolution spectra for this transition. They conclude that this transition correlates with the lowest energy transition for the analogous MnH molecule, and they have assigned it as the b 5 Π−a 5 Σ band system of MnF . If this is correct, then the vibrational constants for the upper state would be approximately ω e = 625.97 cm -1 and ω e x e = 3.20 cm -1 .…”
Section: Resultsmentioning
confidence: 92%
“…They conclude that this transition correlates with the lowest energy transition for the analogous MnH molecule, 45 and they have assigned it as the b 5 Π-a 5 Σ band system of MnF. 46 If this is correct, then the vibrational constants for the upper state would be approximately ω e ) 625.97 cm -1 and ω e x e ) 3.20 cm -1 . However, reaction energetics (see below) suggest that the lower state of this transition could lie ∼2000 cm -1 below the lower state of the d band system.…”
The chemiluminescent reactions between an agglomerated flux of entrained manganese vapor (atoms and small manganese molecules) and halogen vapor (chlorine or fluorine) have been investigated under multiple collision conditions. Both reaction groups produce emission features that are readily correlated with manganese atom transitions, manganese(I) halide molecular emission, and broad features centered at 464, 530, and 720 nm which might be attributed to the manganese cluster halides or to manganese dimer. Chemical reactions involving manganese atoms and small manganese clusters are required to explain the observed emission features. The energetics of several possible metal atom, dimer, and trimer reactions are considered and correlated with the observed emission features. The energetics of some of these reactions are used to estimate the a 5 Σ-X 7 Σ energy separation in MnF. This value, 2500 ( 500 cm -1 , is consistent with the value of 1743 cm -1 determined for MnH and a value of 3000 ( 500 cm -1 estimated previously for MnF. Vibrationally resolved emission features are observed for five previously investigated MnF transitions. While limited information was obtained for the system a (350 nm), c (504 nm), or d (690 nm) transitions, revised vibrational analyses for the b (495 nm) and the e (832 nm) band systems of MnF are presented. The b system bands are found to be blue degraded, with a vibrational analysis suggesting that the observed transition terminates in the X 7 Σ ground state. Twenty bands belonging to the origin sequence of the e system have been identified and fit using a nonlinear least squares analysis. Energetic arguments dictate that the lower state of this transition must be either the ground state or an electronic state differing little in energy from the ground state.
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