S. Paddi Reddy, W. Ivancic, V. Malathy Devi, A. Baldacci, K. Narahari Rao, A. W. Mantz, and R. S. Eng, "Tunable diode laser spectroscopy in the infrared: some practical considerations of techniques and calibration with ν2 lines of HCN," Appl. Opt. 18, 1350-1354 (1979)
A tunable diode laser has been incorporated as a source in an operating high resolution vacuum grating spectrometer. The advantages of such a system for recording molecular spectra have been elaborated. In the process of developing this system, several practical problems came about, and it has been considered useful to document the manner in which they have been resolved. In particular, for work in the region of 15 μm, it was advantageous to develop an air-spaced Fabry-Perot etalon to record fringes simultaneously with the scanning of molecular spectra. This was successfully done, and the ν2 band lines of the HCN molecule at 14 μm have proved to be ideally suited for determining the fringe spacing spectroscopically.
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Calculated Vacuum Wavenumbers a (cm−1) for the ν2 Band of H12C14N b
J
R(J)
P(J)
Q(J)
0
714.9371
1
717.8927
711.9956
2
720.8478
706.0678
712.0248
3
723.8023
703.1109
712.0686
4
726.7561
700.1537
712.1269
5
729.7093
697.1965
712.1999
6
732.6616
694.2392
712.2874
7
735.6131
691.2820
712.3895
8
738.5636
688.3249
712.5061
9
741.5130
685.3679
712.6371
10
744.4614
682.4112
712.7827
11
747.4086
679.4548
712.9428
12
750.3546
676.4988
713.1172
13
753.2992
673.5431
713.3061
14
756.2424
670.5880
713.5093
15
759.1842
667.6335
713.7269
16
762.1244
664.6795
713.9587
17
765.0629
661.7263
714.2049
18
767.9998
658.7738
714.4652
19
770.9348
655.8221
714.7397
20
773.8680
652.8712
715.0282
21
776.7993
649.9213
715.3308
22
779.7285
646.9724
715.6475
23
782.6555
644.0245
715.9780
24
785.5804
641.0777
716.3225
25
788.5030
638.1321
716.6808
26
791.4233
635.1877
717.0528
27
794.3411
632.2445
717.4385
28
797.2564
629.3027
717.8379
29
800.1690
626.3623
718.2509
30
803.0790
623.4233
718.6773
Expressions used to calculate the P, R, and Q branches for the ν2 band of H12C14 N:
Since some of the higher order distortion terms were omitted in deriving the wavenumbers given in Table II of Ref. 1, it is recommended that the present set of wavenumbers be used for the ν2 band of H12C14N. They are consistent with the experimental data available in Refs. 3, 4, and 5.
Calculated by using Eq. (A5a).
Calculated by using Eq. (A5b).
Calculated by using Eq. (A6a).
Calculated by using Eq. (A6b).
Wavelength dependent, value is for 10 μm.
Nearly wavelength independent from 3 μm to 20 μm. We measured 0.016548 ± 0.000030 cm−1 for a 30.09-cm etalon and 0.029851 ± 0.000034 cm−1 for a 16.67-cm etalon at 712 cm−1, which correspond to 0.04973 cm−1 and 0.049762 cm−1, respectively, when normalized to a 10-cm air path.
Tables (2)
Table I
Calculated Vacuum Wavenumbers a (cm−1) for the ν2 Band of H12C14N b
J
R(J)
P(J)
Q(J)
0
714.9371
1
717.8927
711.9956
2
720.8478
706.0678
712.0248
3
723.8023
703.1109
712.0686
4
726.7561
700.1537
712.1269
5
729.7093
697.1965
712.1999
6
732.6616
694.2392
712.2874
7
735.6131
691.2820
712.3895
8
738.5636
688.3249
712.5061
9
741.5130
685.3679
712.6371
10
744.4614
682.4112
712.7827
11
747.4086
679.4548
712.9428
12
750.3546
676.4988
713.1172
13
753.2992
673.5431
713.3061
14
756.2424
670.5880
713.5093
15
759.1842
667.6335
713.7269
16
762.1244
664.6795
713.9587
17
765.0629
661.7263
714.2049
18
767.9998
658.7738
714.4652
19
770.9348
655.8221
714.7397
20
773.8680
652.8712
715.0282
21
776.7993
649.9213
715.3308
22
779.7285
646.9724
715.6475
23
782.6555
644.0245
715.9780
24
785.5804
641.0777
716.3225
25
788.5030
638.1321
716.6808
26
791.4233
635.1877
717.0528
27
794.3411
632.2445
717.4385
28
797.2564
629.3027
717.8379
29
800.1690
626.3623
718.2509
30
803.0790
623.4233
718.6773
Expressions used to calculate the P, R, and Q branches for the ν2 band of H12C14 N:
Since some of the higher order distortion terms were omitted in deriving the wavenumbers given in Table II of Ref. 1, it is recommended that the present set of wavenumbers be used for the ν2 band of H12C14N. They are consistent with the experimental data available in Refs. 3, 4, and 5.
Calculated by using Eq. (A5a).
Calculated by using Eq. (A5b).
Calculated by using Eq. (A6a).
Calculated by using Eq. (A6b).
Wavelength dependent, value is for 10 μm.
Nearly wavelength independent from 3 μm to 20 μm. We measured 0.016548 ± 0.000030 cm−1 for a 30.09-cm etalon and 0.029851 ± 0.000034 cm−1 for a 16.67-cm etalon at 712 cm−1, which correspond to 0.04973 cm−1 and 0.049762 cm−1, respectively, when normalized to a 10-cm air path.