Robert F. Stamm and C. F. Salzman, "Photoelectric Raman Spectrometer with Automatic Range Changing. II. Conversion of Perkin-Elmer Infrared Instrument to Grating Type," J. Opt. Soc. Am. 43, 126-137 (1953)
A Perkin-Elmer model 12 infrared spectrometer has been converted to a plane grating spectrometer for recording Raman spectra photoelectrically. The light source is a Toronto-type, helical mercury arc which illuminates the sample (either 4.5 cc or 9 cc) contained in a vertical, cylindrical tube. The sample tubes are provided with back-surface, concave mirrors (held in the rear of the tubes and integral with the stoppers) thereby doubling the intensity. The difficulties experienced with grating ghosts are discussed along with the requirements for the grating. The fine structure of the CCl4 459 cm−1 and C6H6 992-cm−1 lines can be resolved using a 9-cc sample. With reference to 992 of benzene, a signal-to noise ratio of 120:0.15 can be achieved with a time constant of
and permits spectra to be obtained at a rate of 0.83 cm−1 per sec with intensity ratios correct to within ±1 percent.
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Relative speeds of spectrometers, compared under conditions of constant resolution at 4500A. (The meaning of the parenthetical entries is given in the text.)
No.
A (cm2)
h(cm)
F(cm)
h/F
D×104 (rad/A)
T
[w/(k×Bλ)] ×105
1
44.2
1.0 (1.62)
27.0
0.037 (0.06)
1.26
0.40
8.2 (13.3)
2
28.3
2.2 (3.96)
66.0
0.033 (0.06)
0.65
0.65
4.0 (7.2)
3
17.6
0.44 (0.72)
12.0
0.037 (0.06)
1.6
0.30
3.2 (5.2)
4
146.7
1.0 (14.4)
240
0.0042 (0.06)
1.26
0.36
2.8 (40.0)
5
137.1
0.6 (6.0)
100
0.006 (0.06)
0.629
0.44
2.3 (23.0)
6
43.0
0.6 (6.0)
100
0.006 (0.06)
1.6
0.39
1.6 (16.0)
7
49.0
0.53 (5.52)
92.0
0.0058 (0.06)
1.6
0.24
1.2 (12.0)
Table II
Sagittas to be expected in grating spectrometer;a d1 signifies 15 000/inch, N = 2; d2 signifies 1200/mm, N = 1; h = 5 mm, f = 270 mm, α = 18° or 14° off axis.
λ(A)
4358
4780
5200
d1
d2
d1
d2
d1
d2
14°55′
16°24′
16°40′
17°53′
18°11′
σ(p–g)18°(μ)
4.0
3.5
1.4
0.9
−1.3
−1.8
σ(p–g)14°(μ)
−2.3
−2.7
−4.9
−5.3
−7.5
−8.0
These slight degrees of curvature should not be troublesome when using slit widths of 33μ.
Table III
Intensities of Raman lines relative to Rayleigh line.a
The values for benzene (among others) have also been obtained photoelectrically by J. Y. Chien and P. Bender [J. Chem. Phys. 15, 376 (1947)]. The present values are not in good agreement with their results. In the case of C6H6 the millivolt values for 992 cm−1 and 4358A were 146.2 and 35 330, respectively (corrected). (The intensities are values above background.) In order to compare intensities so widely separated, the ratios of the various grid resistors were determined; also, corrections for nonlinearity of the amplifier were applied. Corrections for changing response as a function of wavelength have not been applied.
Veerabhadra Rao, Z. Physik. 97, 154 (1935).
Table IV
Speed of response to Speedomax G recorder. (First 10 mv = 10 inches.)
E(mv)
10
30
50
80
120
180
t(sec)
1.3
2.6
3.5
4.2
4.7
4.9
Table V
Intensity ratios and influence of scanning rate. Toluene, 9.5 cc, mirror, 51.0 volts/stage, 109 ohms, 0.5 sec time constant, 3.7 cm−1 (25μ) slits. [A, B, and C at 0.83, 1.7, and 3.3 cm−1/sec, respectively; A1B1, and C1 give E/E(Δν622); B2 and C2 give E/EA for corresponding lines.]
Peak occurred close to 10 mv border; difficult to judge true value because of the closeness of the lines at this high speed.
Tables (5)
Table I
Relative speeds of spectrometers, compared under conditions of constant resolution at 4500A. (The meaning of the parenthetical entries is given in the text.)
No.
A (cm2)
h(cm)
F(cm)
h/F
D×104 (rad/A)
T
[w/(k×Bλ)] ×105
1
44.2
1.0 (1.62)
27.0
0.037 (0.06)
1.26
0.40
8.2 (13.3)
2
28.3
2.2 (3.96)
66.0
0.033 (0.06)
0.65
0.65
4.0 (7.2)
3
17.6
0.44 (0.72)
12.0
0.037 (0.06)
1.6
0.30
3.2 (5.2)
4
146.7
1.0 (14.4)
240
0.0042 (0.06)
1.26
0.36
2.8 (40.0)
5
137.1
0.6 (6.0)
100
0.006 (0.06)
0.629
0.44
2.3 (23.0)
6
43.0
0.6 (6.0)
100
0.006 (0.06)
1.6
0.39
1.6 (16.0)
7
49.0
0.53 (5.52)
92.0
0.0058 (0.06)
1.6
0.24
1.2 (12.0)
Table II
Sagittas to be expected in grating spectrometer;a d1 signifies 15 000/inch, N = 2; d2 signifies 1200/mm, N = 1; h = 5 mm, f = 270 mm, α = 18° or 14° off axis.
λ(A)
4358
4780
5200
d1
d2
d1
d2
d1
d2
14°55′
16°24′
16°40′
17°53′
18°11′
σ(p–g)18°(μ)
4.0
3.5
1.4
0.9
−1.3
−1.8
σ(p–g)14°(μ)
−2.3
−2.7
−4.9
−5.3
−7.5
−8.0
These slight degrees of curvature should not be troublesome when using slit widths of 33μ.
Table III
Intensities of Raman lines relative to Rayleigh line.a
The values for benzene (among others) have also been obtained photoelectrically by J. Y. Chien and P. Bender [J. Chem. Phys. 15, 376 (1947)]. The present values are not in good agreement with their results. In the case of C6H6 the millivolt values for 992 cm−1 and 4358A were 146.2 and 35 330, respectively (corrected). (The intensities are values above background.) In order to compare intensities so widely separated, the ratios of the various grid resistors were determined; also, corrections for nonlinearity of the amplifier were applied. Corrections for changing response as a function of wavelength have not been applied.
Veerabhadra Rao, Z. Physik. 97, 154 (1935).
Table IV
Speed of response to Speedomax G recorder. (First 10 mv = 10 inches.)
E(mv)
10
30
50
80
120
180
t(sec)
1.3
2.6
3.5
4.2
4.7
4.9
Table V
Intensity ratios and influence of scanning rate. Toluene, 9.5 cc, mirror, 51.0 volts/stage, 109 ohms, 0.5 sec time constant, 3.7 cm−1 (25μ) slits. [A, B, and C at 0.83, 1.7, and 3.3 cm−1/sec, respectively; A1B1, and C1 give E/E(Δν622); B2 and C2 give E/EA for corresponding lines.]
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