W. Ubachs, K. S. E. Eikema, W. Hogervorst, and P. C. Cacciani, "Narrow-band tunable extreme-ultraviolet laser source for lifetime measurements and precision spectroscopy," J. Opt. Soc. Am. B 14, 2469-2476 (1997)
A narrow-band, extreme-ultraviolet laser source is developed that has continuous tunability in the range 96–97.5 nm and a bandwidth below 250 MHz. The versatility of the radiation source is demonstrated in two applications. Accurate values for lifetimes of highly excited molecular quantum states are determined from line-broadening measurements in three electronic states of CO:
state ( components, ),
state (
components, ), and
state
The application of the source in metrology in the extreme-ultraviolet domain is demonstrated by the highly accurate, absolute calibration of narrow resonances in CO. These molecular lines can be used for future reference standards at these short wavelengths. From accurately determined minute frequency shifts near the accidentally predissociated level of the
state the perturber state is characterized as a yet unidentified Rydberg state with an origin at It is demonstrated that molecular spectroscopy in the extreme-ultraviolet domain at megahertz precision is possible.
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Observed Linewidths Derived Natural Widths Γ, and Calculated Natural Lifetimes τ for Various States in CO
State
(MHz)
Γ (MHz)
τ (ps)
Table 2
Hyperfine Components Calibrated in the Present Studya
Iodine Line
Frequency (MHz)
Frequency
Atlas
(16–1)
515 827 579.5(40)
17 206.15598 (13)
1425
(18–2)
515 870 592.7 (40)
17 207.59075 (13)
1430
(16–1)
515 889 490.4 (40)
17 208.22111 (13)
1434
(16–1)
515 909 718.2 (40)
17 208.89583 (13)
1438
(18–2)
515 925 934.8 (40)
17 209.43676 (13)
1440
(16–1)
515 950 679.2 (40)
17 210.26215 (13)
1445
(16–1)
515 970 647.8 (40)
17 210.92823 (13)
1448
(18–2)
515 980 528.1 (50)
17 211.25780 (17)
1449
(17–1)
515 991 989.1 (50)
17 211.64010 (17)
1451
(14–0)
516 001 716.4 (60)
17 211.96456 (20)
1453
(18–2)
516 008 245.5 (50)
17 212.18235 (17)
1455
(16–1)
516 011 235.3 (50)
17 212.28208 (17)
1457
(16–1)
516 030 852.3 (50)
17 212.93643 (17)
1459
(18–2)
516 034 479.8 (50)
17 213.05743 (17)
1460
Values are a result of relative frequency measurements with respect to the (14–0)
component, determined by Sansonetti at 515 816 575.64 MHz.14 The numbers in the last column refer to the identification of Doppler-broadened lines in the
atlas.6
Table 3
Observed and Calculated Line Positions (in ) of the Lines of the – (0,0) Band of at a
Transition Frequency
Observed–Calculated
(a)
(b)
1
0.0026
0.0001
2
0.0024
0.0001
3
0.0017
4
0.0024
0.0005
5
0.0025
6
0.0072
7
–
–
–
8
0.0010
9
0.0011
10
0.0009
11
12
13
14
15
16
17
0.02
0.03
18
0.05
0.05
19
0.07
0.06
20
0.08
0.05
22
0.12
0.05
Values for levels are taken from Ref. 1. Values in (a) and (b) refer to models for analyzing the data (see text).
Table 4
Frequency Separations between Lines of the (0, 0) Band of CO and Deviations from a Least-Squares Fita
Molecular Constants for Components of the State, Resulting from a Least-Squares Fit Including All Data from Tables 3 and 4a
Constant
Model
(a)
(b)
103 271.787 (4)
103 271.7870 (5)
1.9599 (1)
1.95978 (2)
–
0.22 (1)
(pert)
–
103 266.92 (3)
(pert)
–
2.051 (1)
Values are given in inverse centimeters.
Tables (5)
Table 1
Observed Linewidths Derived Natural Widths Γ, and Calculated Natural Lifetimes τ for Various States in CO
State
(MHz)
Γ (MHz)
τ (ps)
Table 2
Hyperfine Components Calibrated in the Present Studya
Iodine Line
Frequency (MHz)
Frequency
Atlas
(16–1)
515 827 579.5(40)
17 206.15598 (13)
1425
(18–2)
515 870 592.7 (40)
17 207.59075 (13)
1430
(16–1)
515 889 490.4 (40)
17 208.22111 (13)
1434
(16–1)
515 909 718.2 (40)
17 208.89583 (13)
1438
(18–2)
515 925 934.8 (40)
17 209.43676 (13)
1440
(16–1)
515 950 679.2 (40)
17 210.26215 (13)
1445
(16–1)
515 970 647.8 (40)
17 210.92823 (13)
1448
(18–2)
515 980 528.1 (50)
17 211.25780 (17)
1449
(17–1)
515 991 989.1 (50)
17 211.64010 (17)
1451
(14–0)
516 001 716.4 (60)
17 211.96456 (20)
1453
(18–2)
516 008 245.5 (50)
17 212.18235 (17)
1455
(16–1)
516 011 235.3 (50)
17 212.28208 (17)
1457
(16–1)
516 030 852.3 (50)
17 212.93643 (17)
1459
(18–2)
516 034 479.8 (50)
17 213.05743 (17)
1460
Values are a result of relative frequency measurements with respect to the (14–0)
component, determined by Sansonetti at 515 816 575.64 MHz.14 The numbers in the last column refer to the identification of Doppler-broadened lines in the
atlas.6
Table 3
Observed and Calculated Line Positions (in ) of the Lines of the – (0,0) Band of at a
Transition Frequency
Observed–Calculated
(a)
(b)
1
0.0026
0.0001
2
0.0024
0.0001
3
0.0017
4
0.0024
0.0005
5
0.0025
6
0.0072
7
–
–
–
8
0.0010
9
0.0011
10
0.0009
11
12
13
14
15
16
17
0.02
0.03
18
0.05
0.05
19
0.07
0.06
20
0.08
0.05
22
0.12
0.05
Values for levels are taken from Ref. 1. Values in (a) and (b) refer to models for analyzing the data (see text).
Table 4
Frequency Separations between Lines of the (0, 0) Band of CO and Deviations from a Least-Squares Fita