berkowitz_1977#
J. Berkowitz and J. H. D. Eland, “Photoionization of N2O: Mechanisms of photoionization and ion dissociation”, J. Chem. Phys. 67, 2740 (1977)
Source record · Catalogue · Review register
DOI: 10.1063/1.435188
Source kind: measurement
Recorded technique: Photoionisation mass spectrometry with a 3 m normal-incidence monochromator (helium Hopfield continuum) and a quadrupole mass spectrometer, photon resolution 0.07-0.14 A FWHM: photoion yield curves of N2O+, NO+, O+, N2+ and N+ from the threshold to 600 A, and of 14NO+ and 15NO+ from 14N15NO (1 m monochromator, about 0.7 A, magnetic mass spectrometer). Commercial N2O, used without purification; the sample temperature is not stated (pp. 2740-2741).
Materials in structured entries: N2O
Dataset quantities: appearance_energy, dissociation_time, fragmentation_branching_ratio, ionization_energy
Contents: 16 datasets; 0 formulas.
Curation notes#
PDF pages 2-14 = journal pages 2740-2752 (PDF page 1 is the publisher’s cover sheet). Identity checked on the first page. N2O only.
THE FIRST IONISATION ENERGY (p. 2741): the threshold region of the N2O+ yield (Fig. 1, 0.07 A resolution) ‘has a more-or-less linear portion between 961.72-962.60 A, followed by an exponential tail. This linear region is about 10 times wider than our wavelength resolution ... It is most likely attributable to rotational P, Q, and R branches. For the present we take the midpoint of this linear rise as an approximation to the transition involving rotationless levels, and obtain an ionization potential of 12.886 +- 0.002 eV.’ The final state is the lower spin-orbit component X 2Pi_3/2 (the paper places the 2Pi_1/2 onset near 960.9 A with Callomon & Creutzberg’s spin-orbit splitting of 0.0164 eV). The confidence level of +-0.002 eV is not stated.
EXCITED IONIC STATES (Rydberg-series limits): - A 2Sigma+ (000): ‘we deduce a limit of 16.388 +- 0.001 eV’ (p. 2742; Table I), by extrapolating four series (nd pi, ns sigma, nd sigma, np sigma), ‘greatest weight being given to the high Rydberg member of the nd pi series’. Extracted. - A 2Sigma+ (100) 16.544 +- 0.001 eV and (001) 16.692 +- 0.001 eV (Table II, p. 2743): notes only (vibrationally excited ion). - C 2Sigma+: five series ‘all converging to 20.105 +- 0.002 eV, the ionization potential of the C 2Sigma+ state’ (p. 2746; Table VI). Extracted.
QUOTED VALUES (notes): Tanaka et al. (Ref. 5), photographic absorption: X 2Pi_3/2 limit 12.88 eV, 2Pi_1/2 12.92_7 eV (= 959.1 A), spin-orbit 0.038 eV; A-state limits 16.38_6 and 16.39_1 eV (series III and IV); He I photoelectron spectrum (Turner et al.): the A-state ionisation potential 16.39 eV, nu1 ~ 1350, nu3 ~ 2460 cm^-1 (Callomon & Creutzberg: 1345.52 and 2451 cm^-1) (pp. 2741-2742).
APPEARANCE ENERGIES (TC-965; datasets ae_NOplus and ae_Nplus): NO+ first seen very weakly at ~839.5 A = 14.77 eV and with a threshold at ~828 A = 14.97 eV, ‘substantially above the thermochemical threshold for this process (14.19 eV)’ (pp. 2742-2743); an abrupt rise of NO+ at ~749 A = 16.55 eV, the onset of N2O+ A 2Sigma+ (100), none at A (000) (p. 2743). O+: ‘The threshold at ~813 A is essentially the thermochemical threshold’ (p. 2745; no energy printed, not taken). N+ rises abruptly from 617.6 A = 20.075 eV, the linear rise 617.60-616.85 A (20.075-20.199 eV) levelling off at 20.100 eV, against the 0 K thermochemical onset 19.494 eV = 636.0 A (p. 2748). N2+ ‘first appears at the thermochemical threshold, which is at slightly lower energy than the adiabatic onset of the B state’ (p. 2749; no number). Electron-impact thresholds of the metastable N2O+ -> NO+ + N, 15.1 +- 0.2 eV (Ref. 10) and 15.7 +- 0.5 eV (Ref. 11), are quoted (p. 2743), not taken.
STATES AND THEIR FRAGMENTS (the paper’s assignments, pp. 2742-2751): - X 2Pi: stable (N2O+). - 4A’’ (calculated by Hopper, not observed directly), reached by autoionisation of the Rydberg states below A: levels below 15.25 eV dissociate slowly (the ion survives ~3 x 10^-7 s, ‘encompassing ~10^5 vibrations’, p. 2745), with isotopic scrambling, to NO+ + N; higher levels dissociate fast to O+ + N2, ‘favoring O+ by a 3:1 margin’ (p. 2750); ‘The O+/NO+ ratio rises fairly smoothly from threshold, and reaches an essentially constant value of 3 below 780 A’ (p. 2745; dataset text_Oplus_over_NOplus). - A 2Sigma+ (000): no dissociation (no NO+ step). A (100) and above: predissociates to NO+ + N (ground state), unscrambled, NO+ the only product; the ion spends ~10^-7 s in A before predissociating (p. 2745). - B 2Pi: NO+(1Sigma+) + N(2D) and N2+(2Sigma_g+) + O(3P); no O+; the N2+ share grows and the scrambling falls with energy (Table VII; p. 2749, p. 2750). - C 2Sigma+: NO+, N+, N2+ and O+; from the steps at its threshold ‘a branching ratio from the C state to NO+, N+, N2+, and O+ as ~5.7:2.0:2.1:0.2’ (p. 2749, checked on the page). Table VII’s C row prints NO+ 57*, N2+ 20*, N+ 21*, O+ 2.2*: the text and the table exchange N+ and N2+ (TC-965). ‘The dissociations must all be quite rapid’ (p. 2751). The O+ spin-allowed channel opens at 651 A.
AUTOIONISATION BRANCHING TO IONIC STATES (notes only; no quantity holds the branching of a resonance to the ion’s states): A-state Rydbergs branch at most ~7 % to 4A’’, 93 % to X; B-state Rydbergs ~25 % to 4A’’, the rest mainly to X (p. 2751); C-state Rydbergs (Table VIII, % to X, A, B, 4A’’): np sigma 76, 0, 22, 1.6 (members well above B only; Cook et al. would give ~6 % to A); np pi 53, 30, 17, 0; nd sigma 81, 5, 13, 1; nd pi 60, 4, 34, 2; ns sigma -, 64, 34, 2 (the X cell blank, as printed). Table III gives the A-state series’ preferences in words.
TABLE VII ROWS NOT TAKEN (no N2O+ entry, so no stated reference; amplitudes, *): B 2Pi lower energies 705-685 A: NO+ 20, N2+ 5.6, 15NO+/14NO+ ~6; B 2Pi higher energies 685-640 A: NO+ 20, N2+ 16, ~16; C 2Sigma+ (0,0,0) 618 A: NO+ 57, N2+ 20, N+ 21, O+ 2.2, >= 14. The 15NO+/14NO+ column of the other rows (~10, ~10, -, 7.7, 8.6, 9.1, -, -) is the ratio of the unscrambled to the scrambled NO+ of 14N15NO, not a channel of N2O; below the A (100) threshold the autoionisation features in 15NO+ are ‘only ~ four times as intense as those in 14NO+’ (p. 2743).
NOT EXTRACTED: Tables I, II, VI (Rydberg wavelengths and effective quantum numbers), III and VIII (series characteristics: nd pi, ns sigma, nd sigma, np sigma, np pi with defects 0.05, 0.95, 0.23, 0.65, 0.61 for A), V (a B-state Rydberg vibrational progression). The ion yield curves (Figs. 1-5) are raster scans and are not digitised.
Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
berkowitz_1977/adiabatic_N2O#
{
"id": "adiabatic_N2O",
"material": "N2O",
"table": "text",
"quantity": "ionization_energy",
"unit": "eV",
"abscissa": "label",
"use": "primary",
"parameters": {
"kind": "adiabatic",
"final_state": "X 2Pi_3/2 (000), rotationless (approximation)"
},
"uncertainty": {
"column": true,
"level": "not stated"
}
}
1 inline points in the source record.
p. 2741: the midpoint of the linear rise of the N2O+ yield (961.72-962.60 A), ‘as an approximation to the transition involving rotationless levels ... an ionization potential of 12.886 +- 0.002 eV’. To the lower spin-orbit component X 2Pi_3/2. Level of +-0.002 not stated.
berkowitz_1977/A_state_N2O#
{
"id": "A_state_N2O",
"material": "N2O",
"table": "text",
"quantity": "ionization_energy",
"unit": "eV",
"abscissa": "label",
"use": "primary",
"parameters": {
"kind": "adiabatic",
"final_state": "A 2Sigma+ (000)"
},
"uncertainty": {
"column": true,
"level": "not stated"
}
}
1 inline points in the source record.
p. 2742 (and Table I): the common limit of the Rydberg series converging on A 2Sigma+ (000), 16.388 +- 0.001 eV. Level not stated.
berkowitz_1977/C_state_N2O#
{
"id": "C_state_N2O",
"material": "N2O",
"table": "text",
"quantity": "ionization_energy",
"unit": "eV",
"abscissa": "label",
"use": "primary",
"parameters": {
"kind": "adiabatic",
"final_state": "C 2Sigma+ (Rydberg-series limit)"
},
"uncertainty": {
"column": true,
"level": "not stated"
}
}
1 inline points in the source record.
p. 2746 (and Table VI’s caption): five Rydberg series ‘all converging to 20.105 +- 0.002 eV, the ionization potential of the C 2Sigma+ state’. The vibrational level of the limit is not stated (the series are assigned to the state, not to a vibrational level). Level not stated.
berkowitz_1977/ae_NOplus#
{
"id": "ae_NOplus",
"material": "N2O",
"table": "text",
"quantity": "appearance_energy",
"unit": "eV",
"abscissa": "label",
"use": "primary",
"parameters": {
"fragment": "NO+"
}
}
2 inline points in the source record.
pp. 2742-2743 (TC-965): ‘NO+ is first observed, very weakly, at ~ 839.5 A = 14.77 eV, and with considerably greater intensity at a threshold of ~ 828 A = 14.97 eV. This is substantially above the thermochemical threshold for this process (14.19 eV)’. The paper’s mechanism: autoionisation of Rydberg states to the slowly dissociating 4A’’ state, the ion surviving ~3e-7 s. The eV values are the paper’s conversions of the approximate wavelengths; no uncertainty is stated. Photon resolution 0.14 A FWHM (Fig. 2(b)).
berkowitz_1977/ae_Nplus#
{
"id": "ae_Nplus",
"material": "N2O",
"table": "text",
"quantity": "appearance_energy",
"unit": "eV",
"abscissa": "label",
"use": "primary",
"parameters": {
"fragment": "N+"
}
}
1 inline points in the source record.
p. 2748 (TC-965): ‘In the photoion yield curve for N+ (Fig. 5) we note a rather abrupt rise beginning at 617.6 A = 20.075 eV, well above the thermochemical threshold’ (19.494 eV at 0 K, 636.0 A). The linear rise runs 617.60-616.85 A (20.075-20.199 eV) and levels off at 20.100 eV, just below the C 2Sigma+ limit 20.105 eV; the paper relates the width (0.025 eV, about kT) to rotational energy or the thermally populated (010) level. Weak N+ below the onset is attributed partly to collision-induced dissociation. No uncertainty is stated.
berkowitz_1977/t4_Oplus#
{
"id": "t4_Oplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t4_Oplus.csv",
"table": "tbl_130104e0aa54",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "primary",
"parameters": {
"channel": "O+ + N2",
"reference": "N2O+ (the parent ion) = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength (helium Hopfield continuum, 0.14 A FWHM)",
"detection_correction": "none stated (quadrupole mass spectrometer, ion counting)"
}
}
Table IV (p. 2745; TC-965): O+ intensity with N2O+ = 100, at the peak ~798.3 A, the valley ~792 A and the peak ~782 A of the A-state autoionisation (the wavelengths printed with ‘~’). Scale 0.01: the printed numbers are per 100 N2O+. The paper: ‘essentially all of the O+ intensity ... derives from autoionization’, so a 584 A measurement ‘would strongly discriminate against O+’ (p. 2745). No uncertainty is stated.
berkowitz_1977/t4_NOplus#
{
"id": "t4_NOplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t4_NOplus.csv",
"table": "tbl_130104e0aa54",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "primary",
"parameters": {
"channel": "NO+ + N",
"reference": "N2O+ (the parent ion) = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength (helium Hopfield continuum)",
"detection_correction": "none stated"
}
}
Table IV (p. 2745; TC-965): NO+ intensity, printed as ‘15NO+ + 14NO+’ (NO+ ‘both mechanisms’, p. 2745), with N2O+ = 100. The column’s label suggests the sum was taken from the 14N15NO sample (1 m monochromator, ~0.7 A, magnetic mass spectrometer); the paper does not say. Doubt (TC-965): Table IV’s O+/NO+ is 2.5, 1.9 and 4.4 at 798.3, 792 and 782 A, while the text gives an O+/NO+ ratio rising from threshold to an essentially constant 3 below 780 A (p. 2745). No uncertainty is stated.
berkowitz_1977/text_Oplus_over_NOplus#
{
"id": "text_Oplus_over_NOplus",
"material": "N2O",
"table": "text",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"abscissa": "label",
"use": "check",
"parameters": {
"channel": "O+ + N2",
"reference": "NO+ + N",
"excitation": "photoionisation (autoionisation of the A-state Rydberg series to N2O+ 4A'')",
"detection_correction": "none stated"
}
}
1 inline points in the source record.
p. 2745 (TC-965): ‘The O+/NO+ ratio rises fairly smoothly from threshold, and reaches an essentially constant value of 3 below 780 A’; p. 2750: the 4A’’ state’s branching ‘favoring O+ by a 3:1 margin’. One significant figure, no uncertainty stated; above 756 A (below the A (100) onset), where NO+ comes only from 4A’’. Table IV’s ratios at 782-798 A (2.5, 1.9, 4.4) do not show the constancy.
berkowitz_1977/t7_yield_NOplus#
{
"id": "t7_yield_NOplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_yield_NOplus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "primary",
"parameters": {
"channel": "NO+ + N",
"reference": "N2O+ (the parent ion) = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength (helium Hopfield continuum)",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965), the rows without an asterisk: NO+ intensity at 600 A (‘flat’), 660 A (‘valley’) and 668.3 A (‘nd pi peak’), with N2O+ = 100. No uncertainty is stated.
berkowitz_1977/t7_yield_N2plus#
{
"id": "t7_yield_N2plus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_yield_N2plus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "primary",
"parameters": {
"channel": "N2+ + O",
"reference": "N2O+ (the parent ion) = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength (helium Hopfield continuum)",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965), the rows without an asterisk: N2+ intensity with N2O+ = 100. The N2+ curve is of 14N15N+ from 14N15NO in 667-725 A and of normal N2+ in 600-667 A, ‘to minimize the influence of background N2’ (p. 2747). No uncertainty is stated.
berkowitz_1977/t7_yield_Nplus#
{
"id": "t7_yield_Nplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_yield_Nplus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "primary",
"parameters": {
"channel": "N+ + NO",
"reference": "N2O+ (the parent ion) = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength (helium Hopfield continuum)",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965): N+ intensity at 600 A with N2O+ = 100 (3.5); a dash at the other wavelengths (below the 617.6 A onset). No uncertainty is stated.
berkowitz_1977/t7_yield_Oplus#
{
"id": "t7_yield_Oplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_yield_Oplus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "primary",
"parameters": {
"channel": "O+ + N2",
"reference": "N2O+ (the parent ion) = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength (helium Hopfield continuum)",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965), the rows without an asterisk: O+ intensity with N2O+ = 100. No uncertainty is stated.
berkowitz_1977/t7_feature_NOplus#
{
"id": "t7_feature_NOplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_feature_NOplus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "check",
"parameters": {
"channel": "NO+ + N",
"reference": "the same resonance's amplitude in N2O+ = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength, the resonance's amplitude only",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965), the rows with an asterisk: the amplitude (peak height above the continuum) of an autoionising resonance of the C-state Rydberg series in the NO+ channel, with its amplitude in N2O+ = 100 (footnote a). The row id names the series and n*. Not a yield ratio at the wavelength: the continuum under the peak is not included. use = check. No uncertainty is stated.
berkowitz_1977/t7_feature_N2plus#
{
"id": "t7_feature_N2plus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_feature_N2plus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "check",
"parameters": {
"channel": "N2+ + O",
"reference": "the same resonance's amplitude in N2O+ = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength, the resonance's amplitude only",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965), the rows with an asterisk: a resonance’s amplitude in the N2+ channel, with its amplitude in N2O+ = 100 (as t7_feature_NOplus). No uncertainty is stated.
berkowitz_1977/t7_feature_Oplus#
{
"id": "t7_feature_Oplus",
"material": "N2O",
"file": "N2O/berkowitz_1977__t7_feature_Oplus.csv",
"table": "tbl_be3196b2f333",
"quantity": "fragmentation_branching_ratio",
"unit": "1",
"scale": 0.01,
"abscissa": "wavelength",
"abscissa_unit": "angstrom",
"use": "check",
"parameters": {
"channel": "O+ + N2",
"reference": "the same resonance's amplitude in N2O+ = 100, as printed",
"excitation": "photoionisation at the abscissa's wavelength, the resonance's amplitude only",
"detection_correction": "none stated"
}
}
Table VII (p. 2748; TC-965), the rows with an asterisk: a resonance’s amplitude in the O+ channel, with its amplitude in N2O+ = 100 (as t7_feature_NOplus); a dash for the ns sigma n* = 3 resonance at 666.7 A. No uncertainty is stated.
berkowitz_1977/lifetime_4A2_NOplus#
{
"id": "lifetime_4A2_NOplus",
"material": "N2O",
"table": "text",
"quantity": "dissociation_time",
"unit": "s",
"abscissa": "label",
"use": "check",
"parameters": {
"channel": "N2O+ (4A'') -> NO+ + N",
"kind": "lifetime"
}
}
1 inline points in the source record.
p. 2745 (TC-965): ‘the autoionization process requires the N2O+ to survive for ~3 x 10^-7 sec in the quartet state’, an order of magnitude deduced from the metastable-ion observations (the ion must survive ~10^-6 s in the apparatus) and the isotopic scrambling, not a measured decay. For the predissociation from A 2Sigma+ (100) the ion ‘spend[s] most of its time (~10^-7 sec)’ in the A state (same page). Printed as ‘~ 3x 10-7’; no uncertainty.
Formulas#
No formulas are recorded.
Corrections#
No dataset errata are recorded in this source record.
Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.